Just before dawn, by an empty shingle beach, sinister figures move through the gloom. Living shadows, they're dressed all in black, their coats made from long rags, their faces obscured by paint. But their eyes burn brightly as they gather in a circle. If some poor insomniac comes walking the dog now – at 5am on a cold, damp morning – they'll get a massive fright. "Hey-ya!" yell eight men and women as they come together with a loud clash of sticks, and what appears to be a blend of country dancing, martial arts and the mating ritual of raggedy crows. The dance is about sex, there's no mistaking that: one partner stands with legs straddling his stick, holding it upwards from the groin, while the other uses his own stick to bash it about. "It's so much a fertility dance that you'd have to really not know what you were looking at to miss the point," says 47-year-old Laurence Ranger, the squire (a kind of road manager) of Hunters Moon Morris.

Morris dancing is a joke, isn't it, with a hey nonny no? Beardy men with beer bellies prancing about in white stockings, waving hankies? Very twee. But try telling that to the men and women of Hunters Moon, here by the Sussex coast looking like the devilish spawn of Hell's Angels and medieval mummers. They are part of a secret revolution in morris dancing, transforming the most easily lampooned of English eccentricities. Fresh rivalries are emerging, as younger men and women reinvent "the morris" in startling ways – including, as we discover during a mad dash around southern England on May Day, the world's first Gothic morris troupe – or "side".

Dawn on 1 May is when the season starts for dancers who have been practising in pubs and church halls all winter. By the beach at Holywell, the site of an ancient spring in Eastbourne, Hunters Moon are doing a dance that is vigorous, noisy and saucy. And pagan. "Look at it coming up," says a female voice, and she's not talking about her partner's big stick: the sun is beginning to burn orange through heavy grey clouds on the horizon. "That is wonderful."

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The dancers encircle a woman in a long green velvet cloak, who holds up a silver cup. "As the sun rises we meet the summer," she says, beginning a pagan blessing, "and ask that the spirits of the land and sea bring bounty, health and happiness to those within this circle." With that, she passes the cup around like a communion chalice. Later, the remnants of the wine will be poured into the sea, a tribute to the energies of nature, as someone shouts, "I hope that's not Shiraz!"

You don't have to be a pagan to join Hunters Moon, but their symbol is a combination of the moon and the horned man. "A lot of people within the wider morris don't like or accept its connection with the pagan," says Ranger – but for him it is a spiritual experience. "You are grounding yourself, partaking of yourself as a member of the human race, and partaking of the ground you're dancing on." When this finishes, he will be off to work as an office manager. "You get so detached from the natural cycle of life that it is nice to be part of events that remind you. Forming the circle can be quite profound. More so in a quiet place like this than if you're in a town centre getting stick from local yobs."

What about those black faces? "They're a disguise," he explains. "These dances would traditionally have been done during winter by itinerant seasonal labourers who had no work and were busking for money to survive. As they were busking before potential summer employers, or the squire, or the vicar, they didn't want to get recognised."

That's one theory (another links them with Morocco, although everyone agrees it isn't racist). The thing about morris dancing is that everybody thinks they know what it's all about, but nobody really does. The version most of us know was defined by the folklorist Cecil Sharp, who started collecting dances and tunes in 1899, mainly from villages in the Cotswolds. There are many local variations, from the clog-bashing of the northern industrial towns to the cross-dressing Molly Dances of East Anglia, but Sharp's work ensured the Cotswold 'tradition became dominant. Some accuse him of ignoring the sexual and pre-Christian elements of the dance, or cleaning it up for a genteel Edwardian audience – and many sides were sponsored by village churches, whose priests saw them as good, clean fun. But even if he was a censor, Sharp certainly inspired a revival, with new sides being formed all over the country to dance in the Cotswold way.

Morris dancing flourished between the wars, and again during the folk revival of the 1960s and 1970s. But now old-fashioned Cotswold morris is in decline, suffering from ageing dancers and a lack of new recruits. Many of the 800 morris sides in the country are struggling, although they dance on, outside pubs and at festivals every weekend during the summer. And 10 miles inland from the beach, over the downs at Wilmington, the men of Long Man Morris are dancing "Old Tom" this morning in a country lane.

Here are the hanky wavers, in their white stockings, black cord breeches, and white shirts with green-and-gold sashes. Behind them is a field of golden rape, and beyond that the 235ft chalk giant drawn on a hill that gives the side its name. Faces flushed from the exertion, they look like characters from a Thomas Hardy novel. The biggest surprise is the immense skill of the dance. For burly men to carry out such sophisticated steps for an hour or so, while getting those oversize hankies waving in perfect time, requires agility and sharp hand-to-eye co-ordination.

So, what do they think they're up to? Norman Hopson, the 56-year-old squire, is a technical manager for BT but has the no-nonsense manner of a bluff countryman. "Some say the handkerchiefs are there to frighten away spirits, and the same for the bells," he says. "We say they are there to accentuate the movements." Nor is there anything mystical about his experience of dancing: "I see myself as a street entertainer."

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The pagans would like the giant for themselves, but Hopson's men got there first, having been formed 30 years ago. Hopson doesn't see it as a symbol of fertility, or anything else, thank you. "The Long Man is a local landmark," he says. "It's just a carving on a hill. I don't think it has any further significance." The side's bagman, Alan Vaughan, puts it more strongly: "We would go against that pagan idea," he says. "Traditionally, morris dancing has been connected with the church. I personally have danced in Durham Cathedral."

Long Man Morris has 20 members, all male, but it last had a new recruit two years ago. He has still to be given the badges that mark him as a full member. The average age is 50, about two decades older than the next side we go in search of – Wolfshead and Vixen – two hours to the north in Kent.

Wolfshead and Vixen are extraordinary. They are also in the pub, The Good Intent, in a less-than-idyllic part of Rochester, where they have been resting all morning since dancing in the dawn with five other sides on Bluebell Hill.

At first sight they look like a boozy, woozy gathering of the Sisters of Mercy fan club. The Pack In Black, as they call themselves, were the first to adopt that colour alone, when they formed in 1995. The men are blacked-up, in black rags, but with Goth touches: joint-squire Daniel Barnet has a pair of skeletal hands around the brim of his top hat, while others wear piratical silver jewellery and mirror sunglasses. The women are in purple lipstick, black nail varnish and black lace fingerless gloves, with chokers at their throats above bounteous pale cleavages, and flowing dresses made from lace and velvet. Oh and big, clumpy Dr Martens boots. "A lot of sides try to maintain a feeling for a rural tradition that just isn't there any more," says Philip Kane, 48, a poet and story-teller who founded Wolfshead. "Our style is quite urban. That's why people respond to it." Some love the look, others don't, says Diane Eva, a 55-year-old probation officer dressed like Morticia from the Addams Family. "We had a man call our girls – just children – whores of Babylon."

Like Hunters Moon, their performance is based on dances that come, originally, from the borderlands between England and Wales. Border morris was not defined as a style until the 1960s but is now the template for most of the new sides. Wolfshead are the most radical: they don't use many folk tunes, for example, but write their own music, often in minor keys so it is more soulful. "The tradition has to mutate to survive," says Hanna Irwin, who joined at 13 and is now 21. "It's our heritage, but we're putting a twist on it." They're not all Goths in real life, either. "This is a costume," says Mel Barnet, 35, a pharmacist. "It's glamorous, it's sexy, it appeals to young people. Waving hankies just makes them feel silly."

One reason for the recent growth of Border morris is that it is easier to learn (while more spectacular) than other forms. Another is an increase in the number of British neo-pagans, many of whom are drawn to it. "We quite consciously work with ideas of shamanism," says Kane. "It's a form of ritual theatre, a magical space embracing both dancers and audience."

There are radical politics at work too: he sees the dance, and "neo-pagan carnivals" such as the Rochester Sweeps, as a way of resisting the "complacent nostalgia" of Englishness "founded on the detritus of imperialism, Christianity, racism and xenophobia". His England has more primitive, inclusive roots, and for him the morris is a way of expressing that. Or maybe it is just street entertainment, as the Long Man traditionalists insist. Whatever it is, or is becoming, as Wolfshead rouse themselves to dance in the street by broken glass and parked cars, I now know this about the morris: it's no joke.

Hunters Moon

You don't have to be pagan to be a member of Hunters Moon morris, but it must help. Based in Eastbourne, East Sussex, they dance in the boisterous Borders style, with big sticks and lots of whoops. Hunters Moon will appear at the Chippenham Folk Festival in Wiltshire over the second Bank Holiday weekend, with many other morris sides. www.huntersmoonmorris.co.uk

Wolfshead and Vixen

Wolfshead and Vixen are the first Gothic morris side. Members gather at The Good Intent pub in Rochester, Kent, where they practise. Formed in 1995, they bring their own sense of ritual theatre and a modern Gothic style to Borders morris. They will appear around Kent over the summer, but their next major event is the Picnic on the Green in West Peckham, Kent, on 20 July. They can be contacted via their page on MySpace

Long Man

Long Man Morris Men dance for fun and to preserve the tradition, rather than for spiritual reasons. Their style is Cotswold morris, with some local variations. They will be appearing all over Jersey during the May Bank Holiday weekend, at the invitation of a local side. www.longman.org.uk

Tempting fêtes

Little Milton Church Fête

Opened each year by local chef Raymond Blanc, so if you win the raffle, a lunch at Le Manoir aux Quat' Saisons is yours. Pony rides and a brass band keep things lively.

7 June, Oxfordshire, free entry

Granby Fête

Microbreweries offer locally brewed tipples, while the WI takes care of preserves, pickles and home-made cakes. The local farmer provides beef burgers, and there's face-painting for the children.

21 June, Nottinghamshire, free entry

Carlton Feast

An Olympic-themed float procession will make its way to the grounds of Carlton Towers. The local WI serves up sarnies and cakes, while fairground rides will keep kids happy.

21 June, Yorkshire, £1 for adults, 50p for kids

Ebernoe Horn Fair

An annual day-long clash between Ebernoe Cricket Club and a local rival takes place on the village green, while sheep are roasted in an open fire pit, and trestle tables groan with home-made cakes and cream teas.

15 July, free entry, West Sussex

Earl Soham Fête

Home-made cakes, toy and bric-a-brac stalls are the background to a mini railway track that snakes its way round the grounds of a large house that overlooks the village green.

2 August, Suffolk, free entry

Loders Manor Fête

Children are well catered for at this fête held in the grounds of Viscount Hood's ancestral home, with fancy-dress competitions, ferret-racing and side shows on offer.

2 August, West Dorset, £1 for adults, free for kids, tel: 01308 423 127

Chawton Village Fête

Jane Austen's home village treats visitors to falconry displays, a Punch & Judy show, a vegetable-growing competition and a spectacular spread of cakes in the village hall.

9 August, Hampshire, free entry, www.chawton.info

Queen's Park Day

A village atmosphere prevails in this north London park, as visitors enjoy falconry displays, a strong-man show, and fancy-dress and fruit-cake competitions, all to the accompaniment of a steel band.

14 September, NW6, free entry, www.qpara.org

Adam Jacques