Sharon Horgan doesn’t especially enjoy watching herself on screen any more. She feels an awkwardness that, she thinks, comes from years of sitting in edit suites scrutinising take after take of television programmes she has created, co-written and starred in. Shows such as Pulling, a black comedy about three female flatmates that first aired in 2006 and was her breakthrough. And Catastrophe, the Channel 4 series (rejected by the BBC) that she made with Rob Delaney about a one-night stand with long-term effects that ran for four seasons and has been broadcast in 133 countries and now means she has to have clocks in her London offices showing the time in New York and Los Angeles. But Horgan, who is 49 and has eviscerating self-awareness, also accepts that “vanity” might be a factor.

“I just don’t love seeing myself as an older person on screen,” she says, with a snorty half-laugh that seems to punctuate her most radically honest statements. “There’s always a weird transitional period where you go from being able to play a girl who doesn’t know where her life is going to playing the mother of an 18-year-old. The adjustment for that just takes a little bit of time.”

Horgan is sitting in the boardroom of Merman, the production company she founded in 2014 with producer Clelia Mountford. It’s a large, grown-up room with a view of the London Eye and a clutch of awards dotted around, but casually. She’s wearing a black vest, wide-legged jeans and Adidas shelltoes, and looks unfussily chic. “I generally like to pick up my clothes from the floor from the night before and wear them for as long as possible,” she explains. “It’s fine when I’m at home, but if I come in here three days in a row and I’m wearing the same thing, people point it out.”

Facebook Twitter Pinterest Hitting the high notes: with Kristin Scott Thomas in Military Wives. Photograph: Aimee Spinks/Lionsgate UK

We’re here to talk about Military Wives, which she stars in with Kristin Scott Thomas, and in which she plays, as it happens, the mother of an 18-year-old. It’s a dramatisation, by the Full Monty director Peter Cattaneo, of the true story of the women from a Royal Marines base in Devon who formed a choir while their partners were away in Afghanistan and wound up the Christmas No 1 in 2011.

So, has Horgan seen it yet? “I didn’t watch it at the premiere,” she admits. “But my PR lady said, ‘You cannot go into interviews to talk about the film if you haven’t seen it.’ So I got them to send me a screener and I watched it on my laptop, which I’m sure Peter absolutely abhorred.”

I’ve spent years doing things that were always called cult comedies

What did she think? “Kristin and I had the same experience when we read the initial script: it fucked both of us up,” Horgan says. “We knew that if they were the right songs, if they were done in the right way, that this female friendship – the female version of a bromance – could be a really moving and sweet and funny and life-affirming film. So, yeah, when I watched it, I thought: ‘It’s all those things I thought it would be.’”

While Military Wives follows a familiar formula, you would have to have a black heart – something, admittedly, Horgan has been accused of – not to have to wipe away a small tear by the end. Horgan is the best thing about it, undercutting any hoariness with a curl of her lip or a withering aside. (She didn’t officially work on the script, but with Scott Thomas she did “inject a bit of us into it”.) Military Wives probably won’t do the full Full Monty in terms of impact, but there’s a calendar-girls, potato-peel-pie-society market for it. “Different films, but similar ingredients,” says Horgan. “It just makes people feel good.”

Facebook Twitter Pinterest ‘I really want to write about what it is to be a woman of a certain age whose life is changing’: Sharon Horgan wears skirt, top and boots all by Victoria Beckham; rings by Branch on the Park. Photograph: David Yeo/The Observer

Military Wives is a tonal departure for her; “uplifting” and “feel-good” haven’t exactly been in her wheelhouse. Horgan has summed up her work as being “funny and grim”, but what makes her comedy rare is how much she makes you care about her characters, even when they are behaving abominably. The relationship between Rob and Sharon in Catastrophe feels real – screwed up but real. “You let me put my penis in your mouth, but you won’t let me put my T-shirts in your drawer?” Rob notes when they start living together. The interactions between the parents in her BBC2 comedy Motherland are excruciating variations of ones you see at the school gates, especially if you are a bit middle-class. Horgan has an unerring ear and an unsparing eye.

“I watched the trailer for Military Wives with my 16-year-old daughter and she laughed all the way through it,” says Horgan. “And I was like, ‘Fucking cow.’ And she was like, ‘No, it’s great. It’s just funny seeing you with this beautiful song running throughout and then cutting to you on a keyboard and then cutting to you with your head in your hands. It’s just funny. You have to admit it’s funny.’”

It is kind of funny, Horgan concedes. Military Wives is a step change to what she’s done before, but she has her reasons for branching out. Merman exists because Horgan was fed up with coming up with ideas, writing them, and then taking them to someone else to make them. The company started slowly, but in the past five years it has become an industry powerhouse. Its productions are ubiquitous on TV channels and streaming services, and it is known especially for developing new female talent. These include shows that Horgan co-writes, but doesn’t appear in, such as Motherland, and Divorce with Sarah Jessica Parker for HBO, but also Aisling Bea’s This Way Up, Frayed by Sarah Kendall and There She Goes, which won a Bafta for Jessica Hynes. Merman has also moved into drama and films: its first feature, Herself, by Irish writer and actor Clare Dunne, premiered last month at the Sundance Film Festival and was bought by Amazon.

“I’ve spent so many years doing things that were always called cult comedies,” explains Horgan. “So it’s nice to do something that will have a bigger audience. And being cynical and business-minded, it helps your profile when I go into pitches here and in the US. If you’re going in with a writer who is maybe less well known, who you’re wanting people to take a chance on, people give a shit about that.”

Facebook Twitter Pinterest On the rocks: in Catastrophe with Rob Delaney. Photograph: Channel 4

Horgan sounds conflicted. She notes that Catastrophe, as popular as it was, probably had “half the numbers” of a comedy like Derry Girls. She’s dabbled in big studio films before, but in supporting roles, notably the 2018 comedy Game Night, with Jason Bateman and Rachel McAdams, and knows that these parts come with much less control than she’s used to. It appears that Horgan is nailing that hard-to-square feat of allying a rich, diverse creative life with commercial success, but she’s unsure whether to focus her energies on acting or writing or producing or directing, or just to continue, like now, doing all of them.

“The weird thing I fight in myself is going after a mainstream audience and also thinking that I’m not entirely sure I know how to write for a mainstream audience,” she says. “The sweet spot is to do that and to do it well. And to do it in a way that you’re not compromising. But there’s something very intoxicating about creating a show that has widespread appeal. You do want people to see your work.”

At any point, Horgan might be working on a mind-boggling 30 projects. It’s hard not to trace this demented pace to the fact her career kicked off relatively late, in her mid-30s. She was born in east London, but moved to Ireland when she was four. The family settled in County Meath, north of Dublin, where they had a turkey farm. “I wanted to be a performer, but it didn’t feel possible,” she says. “I think that’s why it took so long. I mean, I had a lovely childhood and my parents were super-supportive, but if you’re brought up in a tiny village and your parents are turkey farmers, it doesn’t necessarily equate that you go into show business.”

Horgan went to art college in Dublin, hung out with bands, did some backing singing. “At one gig, this crazy Swiss producer came up to me at the end and was like, ‘I’m gonna make you a star. So, I flew with him to Zurich and he spent the week doing publicity photos, introducing me to people and trying to find out what my talents were.” Horgan laughs, “So, after that week, I was like, ‘Oh well, this is what happens to me. People walk up to me and say, I’m going to make you a star.’ That handicapped me for years.”

I want to take risks – ignore the negative side of my brain and continue to push

Instead, Horgan moved to London and worked at the Jobcentre in Kilburn, north London, for six years in her 20s. She only quit, aged 27, when she was instructed to pick up human excrement from the pavement outside. She moved around squats with Irish friends, before eventually renting a room in co-operative housing with a teacher and a nurse.

“When I moved to London, I think I really was genuinely coming over not to make my fortune, but to be discovered,” she says. “And I literally just got a job in the Jobcentre. I don’t know who I thought was going to discover me there.”

Horgan ultimately poured the energy of this chaotic, feckless period into Pulling, the sitcom she wrote with Dennis Kelly. She and Kelly had worked on sketches together in the 90s, won the BBC New Comedy Award in 2001, and began contributing material to Monkey Dust, Harry Thompson and Shaun Pye’s subversive animated series for BBC Three. The late Thompson (instrumental in launching Have I Got News For You and developing the character Ali G) had a sitcom title, Pulling, but no characters or plot, and suggested that Horgan and Kelly fill in the gaps.

Pulling wasn’t exactly autobiographical, but some true stories found their way in: yes, Horgan once ate a takeaway she found in a phonebox. Around the time that Pulling was coming together, she met Jeremy Rainbird, who worked in advertising. Six months later she was pregnant, and not long after that they were married. They have two children, Sadhbh, 16, and Amer, 11. If some of this feels familiar, it might be because parts of it were the starting point for Catastrophe, which follows the characters Sharon and Rob from messy hook-up to messy, just different, life with children.

We’re evicted from the “posh room” we’re in, which is needed for a meeting, so we scuttle across the landing to a writers’ space. It’s much smaller, there’s no view of the London Eye, and there’s a whiteboard on the wall and a sofa at one end. “There will be a bit of time where you run out of ideas and you just need to lie down,” she says.

Facebook Twitter Pinterest ‘When I write about what’s going on in my life, I connect to it way more’: Sharon Horgan. Photograph: David Yeo/The Observer

While writing Pulling and Catastrophe, she shared a single keyboard with Kelly and Delaney respectively; she and Kelly would share the typing, but with Delaney it was always Horgan. It’s a draining way to work, but it has advantages: you receive immediate, brutal-if-necessary feedback, and there’s the drive of trying to make the other person laugh.

There are occasional rumours that Catastrophe will return in some form, perhaps as a one-off special, but that’s not on Horgan’s schedule. “I’d love to write with Rob again,” she says. “We just fitted so well together. But we also spent five years writing something that was quite intense, and it’s good to step away and do other things. So I’m my own partner right now, and yeah, that’s OK.”

Horgan considers Pulling and Catastrophe as chapter one and two of a trilogy. What form the third installment will take is something she’s wrestling with now. Both professionally and personally, 2019 was a tough year: Catastrophe ended, and so did her marriage to Rainbird. “After Catastrophe, I knew I’d have a period where I was like, ‘I don’t know what the fuck I’m doing,’” she says. “It was grand because I had so many other things, like Motherland and This Way Up and lots of Merman stuff, but I was also like, ‘Shit, I don’t have that thing. I don’t have that idea.’ And I was trying to not give myself a hard time about it, trying to just wait and see what came.”

On Catastrophe, Horgan and Delaney abided by one directive: make nothing up. It was designed to stop them slipping into cliché, and however gruelling it is to stick to, Horgan thinks it’s worth it. “I feel when I write about what’s either going on in my life or has gone on in my life, I just connect to it way more, have more stuff to say,” she says. “It also provides me with a little extra therapy, getting stuff down on the page.

“I really want to write about what it is to be a woman of a certain age whose life is changing,” she goes on. “And I want there to be a teenagers’ element to it. But I don’t want to write about my girls, because I think that’s just not fair. Also, I don’t want to start watching them the way I watch everyone else. You know, when you’re in the moment, but also part of your brain is thinking, ‘I must scribble that down later.’ So I’m trying to find a way round that, probably by giving the kids a different gender.”

Facebook Twitter Pinterest Breakthrough show: 2009’s Pulling. Photograph: Silver River/BBC

Horgan sounds like she is happiest when writing. “It’s like the ultimate escape,” she says. “You open your laptop and immediately you’re somewhere else.” But 2020 is already filling up. he’s in the film adaptation of the hit musical Everybody’s Talking About Jamie, and is about to start shooting a romantic comedy, the Last Drop, opposite Vince Vaughn. She’s also in advanced discussions to direct her first feature, The New World, an adaptation of Chris Adrian and Eli Horowitz’s sci-fi novel.

“I just want some adventures,” she explains. “To do stuff that’s challenging. You can get into a bit of a rut in terms of what you write about and what your safe space is. So yeah, just take a few risks. It’s weird, with the directing thing, I’ve done it a few times, but every time I do it, I think I can’t do it. So it’s like ignoring the negative side of my brain and continuing to push it.

“But then I also want to take my foot off the pedal a bit, so all that doesn’t make any sense,” Horgan continues. Then there’s that half-laugh again: “I want to get my daughter’s GCSEs out the way and come out the other side and have a happy, non-stressful home.”

Military Wives is released on 6 March

Styling by Frederika Lovelle Pank; hair by Hamilton Stansfield at slreps.com using Philip B Haircare; makeup by Justine Jenkins using Delilah Cosmetics