"Alright mate?" A hand tipped with long neon plastic nails, balancing a fag between fingers, reaches out of a trailer door to greet me. It belongs to Lauren Socha, better known as Kelly in Misfits, the foul-mouthed young offender with the power to read your mind and deliver one-liners with immaculate timing. Today, filming the E4 show's third series on London's eerie Thamesmead estate, she's not playing Kelly, though. Except she is. But isn't. Having discovered, at the end of the last run, that they can be bought and sold, the gang's powers have changed. Nothing is quite the way it was. "I'm different people," Socha tries to explain, wary of giving anything away. "Kelly's a chav. I'm not playing a chav, I'm playing someone completely different: upbeat, very excited and a bit weird."

That description of the character-within-a-character she's playing today isn't so far from a self-portrait. Socha talks quickly, tying herself in knots, stating something as cold hard fact one minute, then contradicting herself the next. She says she thinks people who call her a chav are "racist" but uses the word herself all the time. I get the impression that it's pre-emptive, defensive, that she's saying it about herself before anyone else can say it about her. Sitting in a trailer thick with cigarette smoke, she ploughs through endless topics; from class to the fitness of Tom Hardy, and her desire to do period dramas. She's brilliant company: deadpan, tough and, as Misfits fans will have gathered by now, very, very funny.

Lauren Socha with her BAFTA Photograph: Ian West/PA

It's been a very good year for Socha, now 21. In May she took home the Best Supporting Actress Bafta for TV, beating Jessie Wallace, Lynda Baron and Gillian Anderson in the process. "I'm like the hero of Derby," she says. "It's dead nice to know I've achieved something. I love my home and all my mates at home, so it's a really nice feeling." She's proud of where she's from – "Derby born and bred, mate" – and she still tries to go home every weekend she can, just to "chill and have banter and all that". But she doesn't go out in the city any more. "No … no," she says, a little sadly. "You've still got the odd dickhead, cos they're jealous, but ... I won't go into the shitty pub in Derby and purposely get recognised, then get into a fight, because I can't let anyone take me for a twat. I'm not like that."

At school, she says, she was always in trouble. "I didn't give a shit about it. I didn't want to be there. I think the way they teach you is terrible. They're all there for the power and the money and they don't give a fuck about you." She breaks her train of thought to text her mum, then, when she picks it up again, she's reconsidered. "I don't think that's right, and looking back now, I'm totally embarrassed. I went back to the school in February and was just like, I'm so sorry for what I was."

It was three years ago when everything changed for Socha. She was attending an improvisation workshop in Nottingham when she was picked out to star as one of the leads in The Unloved, a feature film by Samantha Morton about a girl growing up in the care system. It brought Socha a Bafta nomination in 2010. "It was a massive open audition, and [Morton] wanted real people. I just wanted to be one of the kids in care. But she took me on a walk and said, 'We really want to give you a bigger part.'"

She followed that with BBC1's excellent, harrowing drama about the Ipswich murders, Five Daughters, and even in Misfits, despite the zingy humour (look out for Socha chewing on the word "brunch" in this season's opener), there's a sadness to her character. Why, I ask, do you think you get cast in these sorts of roles?

Lauren Socha in the Arctic Monkey's video for When The Sun Goes Down

"It's hard to explain," she says. "And obviously I want to do things other than playing a chav or a prostitute or a crackhead. I want to do theatre and I want to do period drama. But I don't know [about] that, because I don't see it. These parts, I've seen it, and I know how it works in a very real way. Does that make sense?" Yes, I say. Do you mean you've had those experiences? "Well, not prostitution and stuff like that, but of course I've seen what's going on. It's sad, but I've seen it. I've seen a lot of drugs – not me, obviously – but I've seen how it affects people. I didn't have the best upbringing. I lost my dad at 16 and I've seen loads of shit in my life, so … I've been there and I've done it."

You'd think Misfits, with its superhero premise, would be a relief for her. But she insists she'd much rather play it straight. "I love playing serious! That's a relief for me. It means something. It sounds dead corny and cheesy, but on a day-to-day basis, you can't just let loose and cry. So as an actress playing those gritty roles, I can play it quite decently. Obviously," she says, mock-offended at the idea, "I don't want to be typecast as a bloody chav all my life."

You wouldn't want to mess with Lauren Socha. But these days, she wouldn't mess with you, either. Having insisted earlier that she's "not a fuckabout", she's determined to make something of herself and her career. She zips through the things she's ready to do next. "I'm ready for theatre. I'm ready for dramas, period stuff, films. I want to achieve everything."

From that, she moves onto a list of who she wants to work with. "Mike Leigh, Kathy Burke, Ray Winstone, those kind of people. Tom Hardy. He's very fit. I fancy him. I heard he's got a girlfriend, but that's alright. Do you mind if I have a fag?" she asks. And then, in an instant, she's gone.

Misfits, 30 October, E4

• This article was amended on 24 October 2011. The original incorrectly named a BBC1 drama about the Ipswich murders as Five Women - the correct title was Five Daughters. This has been corrected.