Tim Fountain: I'm not just a sex freak...

I once signed up for Mary Whitehouse's team. It was at an Oxford Union debate in the 1980s and I thought it'd be boring to speak on the side of progress and liberation. So I volunteered to be on the old bat's side against the tedious Erica Jong and her famous zipless fucks. Then, maddeningly, Mary cried off and I wanted to change sides.

What would Whitehouse have made of the State of the Nation 2008? More particularly, what would she have thought of Tim Fountain's new book, Rude Britannia, "one man's journey round the highways and bi-ways of British sex"? Tim Fountain – hitherto a rather specialist taste – has gone national, inspired, he says, by David Dimbleby's BBC1 programme A Picture of Britain. He wanted to see if people Down Your Way were generally as depraved and kinky as him or whether he was utterly alone.

On 14 January 2005, the Daily Mail shrieked: "Curtain up on depravity: watched by audience of 300, gay actor stages naked sex show with man in a public square". The occasion was Fountain's Royal Court show Sex Addict. In conversation, Fountain is one long torrent of filth, and the Mail's reaction was exactly the one that he's always liked to provoke. (The encounter was less dramatic than it sounds. Fountain and a volunteer stripped to their socks and posed for the cameras against the war memorial, but were too cold to proceed.)

By his own reckoning, Fountain, aged 40, tells me he has slept with something like 40 women and 5,000 men. Difficult to keep score at that scale, you'd think, but he does a calculation which goes 5 per week for 20-odd years. This provokes a number of questions in the liberal bourgeois head, like: aren't you hyping it a bit there – and why? Wouldn't it all be a bit much – and above all why aren't you dead? All of which he then fields very well because he's been asked them endlessly and, as he says, he's a manic over-sharer about that side of life. (Bette Bourne, the star of his new play, remembers a man shouting in the street, "Tim Fountain, get a private life".) The answers are a) yes, and it's not that remarkable except I've gone public about it; b) it's just acting on impulses that lots of people have; and c) he's careful about what he does.

Before the Royal Court affair, Fountain was better known as a playwright who created monologues about remarkable, highly "constructed" personalities. He packaged three people I knew fairly well: Resident Alien in 1999, was based on the work of Quentin Crisp, played by Fountain's favourite actor Bette Bourne (who's a man); Julie Burchill is Away; starring the comedian Jackie Clune, and How to Lose Friends and Alienate People, where Jack Davenport played Toby Young, the IoS's dynamically self-effacing columnist.

According to Fountain's friends, the experience of working with these hugely viewy self-publicists provoked Fountain to claim the spotlight for himself and write Sex Addict, a sort of stage reality show built round Gaydar, the on-line gay contact site. Fountain talked about his sex addiction and its roots, dialled up prospective partners on Gaydar – shown to the audience on giant screens – and asked them to pick his date for him, then reported the encounter in the following day's show. As formats went, it was undeniably ingenious and immediate, and designed to annoy and alarm almost everyone in sight. Not just the Mail, but the famously liberal Royal Court. When the Shy Exhibitionist contact wanted to Do It On The Stage Right Now the result would've broken every law going – that's why they ended out in Sloane Square. The Royal Court had to think of its sponsors, its grants and its landlords. And Gaydar asked him to stop transmitting their subscribers to a wider world.

Now Fountain is claiming to have looked at what real Brits of all kinds get up to now. Out there. And by metropolitan/Southern standards it's very Out There. There's Manchester and Blackpool, Hull, Bradford and Batley (Fountain's from Dewsbury), Glasgow and East Kilbride. In London it's King's Cross, Caledonian Road and Kentish Town. And he goes off to Egypt with a clutch of Northern women sex-tourists. Absolutely no Kensington and Chelsea.

It's hardly scientific – he's not exactly heavy on statistics – but it is compelling and oddly convincing on the new British way of sex. While the story is that the nation is increasingly depraved, trying hard to Be It, not just Dream It any more, the reality is that old habits die hard, and a lot of what he describes sounds like nothing so much as an updated Donald McGill postcard world.

Fountain makes dirty Britain 2007 sound disarmingly funny, because he's disarmingly funny. He comes across as the love-child of Russell Harty (with Alan Bennett a possible godfather and Thora Hird his granny). As a teenager in Dewsbury he believed Bennett's dictum that in Yorkshire life was what happened somewhere else, yet he couldn't be more Northern; everything comes out as Tough Camp funny, in a line of succession that loops around from David Hockney to Lily Savage via Coranora. "Tim is a distinctly Northern soul," says Julie Burchill. "I think he has an incredible writing talent – he's so much more than a sex-freak."

He's got a brilliant ear for a certain kind of dialogue. Thus when one of those Northern women in Egypt says "what's the bloody point of staying in Bolton in the pissing winter when you can live here at a third of the cost and get treated like a queen," you suspect it's resonant with Fountain's Inner Northern Housewife.

He says Brits really are trying to have more casual sex all over the place, and women are learning from gay men in the search for the uncomplicated, uncommitted anonymous encounter. There are all kinds of kinkinesses running riot, from the mass exhibitionism of dogging (car-based sex with an informal audience) in East Kilbride to the world of Furries (group sex between consenting adults dressed in animal costumes).

There's much more of the funny stuff – as it sounds – than the truly hard and nasty. And although there's a fair bit of commercial sex there's nothing about, say, enslaved Eastern European prostitutes, and lots about enthusiastic amateurs.

Try as Brits might for sleek hedonism, Fountain makes it sound as if the hard-wired native passions for panto, drag and dressing-up generally have carried through into 21st-century sex. A lot of what he sees seems to involve trad costuming, class references and all kinds of officious supervision from naked Captain Mainwarings who appoint themselves "torture monitors" and other prefectish roles. There are also lots of sharp references to every kind of superannuated popular culture – soaps, naff presenters, defunct fast-food outlets and hotels – and all the locations seem to have that old synthetic carpet so clagged up it sticks to your shoes.

Other British obsessions bear on the rush for self-expression too. Tacky-snacking, for instance. Fountain is brought low by a floating cheese and tomato sandwich in a giant Jacuzzi in one key set-piece. And he concludes no Englishman can engage in any kind of filth for long without a supply of sausage rolls or vol-au-vents to hand.

The organisation of everything he sees seems to reflect a kind of trainspotter nerdiness where, say, the parking facilities, catering and decoration of the massage parlours reported in punternet.com – the Michelin guide for the sector – attract acres more comment than the girls and their skills.

He plays it for laughs because that's his strength. And also, so you suspect, he's trying to tickle the reader into accepting a much wider sex repertoire – including his own. As his friend, the writer Carol Sarler, says, "he's daring you to purse your lips and get disapproving, but the redeeming thing is the sheer sense of mischief. He's not aggressive and misogynistic in the way some gay men are."

The book's clearly shaped for TV, not exactly Dimbleby, but close to the kind of freak-show television tours that, say, Jon Ronson or Louis Theroux make. The problem is that even Channel 4 could find a lot of this material genuinely hard going – and especially Fountain's personal history rap. It could limit the TV market for an otherwise very telegenic book, full of daft-as-folk set-pieces and potential characters-to-camera. As Toby Young says, "he's extremely clever and very funny and he deserves to be famous for talent not in-your-face gayness."

Fountain certainly strikes one as ambitious and attention-seeking enough for the mainstream. And prodigiously hard-working too. Last year, in parallel with his Rude Britannia progress around the country, he was writing his new play, Rock, which recently opened in London. It's about the invention of Rock Hudson by Henry Willson (played by Bette Bourne), the gay Hollywood agent who gave the world an endless supply of Tabs and Troys, Clints and Rorys, those 1950s film and television beefcake clones who populated the teen beach films and TV westerns. The former Roy Fitzgerald from Ohio was moulded by Willson from a worryingly high-pitched, flappy-handed gay van driver with poor social skills and a terrible wardrobe into the gold standard of Fifties American masculinity: Hudson was Willson's most successful client by a mile. The play's about their relationship, about the building of yet another constructed personality, the changing balance of power and Hudson's eventual desertion to another, safer, more mainstream agent as Willson goes downhill and becomes a reputational risk. It's a strong two-hander about a very odd Pygmalion relationship, sharpened by us all knowing how the Rock Hudson story ends. (Willson was long gone in 1985 when Hudson died of Aids; he'd died penniless in 1978.)

In 2001, Fountain started living with Clune, hitherto a rather politicised lesbian, during the run of Julie Burchill is Away. "I was fed up with sleeping with women," says Clune, "Tim was a half-way house." Clune has gone on to marry and have four children, three of them triplets. Fountain's gone back to the boys, though. He says he's an inadequate heterosexual, a lazy one, who can't cope with all the palaver of dating.

"Tim's guilty secret," says Clune, "is that he's a really sweet boy – an only child – who wants a lot of attention. He sees himself as a scourge of the bourgeoisie because he's giving a window into this unknown sex world, and he's giving all this good quote about it, but the truth is that while he's banging on about perversion-of-the-week I really want to read knitting patterns."

Rude Britannia, By Tim Fountain (Weidenfeld £12.99)