Matthew Horne: Fom Gavin & Stacey to leather-clad psycho

Mathew Horne would like to get one thing straight. "Gavin's much nicer than I am. I'm nothing, nothing like him. I'm not from his world. I don't have a family like that. I don't have a job like that. I don't dress like him. I don't talk like him. I don't have friends like him. I'm nothing like him." Phew. Got that? The actor best known as the romantic hero at the heart of the Bafta-winning sitcom Gavin & Stacey is nothing like his most famous creation.

Funny, he looks quite like Gavin. True, the all-black ensemble he's wearing today – expensive, designer-looking coat, faded jeans, woolly jumper, plimsolls and, a nice fashion-conscious touch, this, neon-yellow skinny belt – is a lot less label-flashy than Gavin's preferred line in spivvy sportswear. And up close, Horne's pixie-ish face looks a little more lined than Gavin's boyish complexion. Plus, there's a campness about Horne as he bounces around on the sofa, tugs at his hair and gesticulates wildly that, you'd imagine, Gavin's boorish best mate, Smithy, would have little truck with.

Alike or not, playing Gavin, the Essex boy who embarks on a sweet romance with Welsh lass Stacey, has gained Horne legions of – mainly young and female – fans. They scrawl all over his MySpace page – "your the best on Gavin and Stacey", "love ur work, plus, ur well lush", "OMG MATT HORNE. Love. Love. Love this dude" – and, when filming in Cardiff, Horne is "more or less mobbed" by them. "Gavin is what a lot of mums would like their sons to be and what a lot of girls would like their boyfriends to be," he sighs. "I'm not great at dealing with it. In London, in every Tube carriage someone will recognise you or say something. You can't walk down the street for very long. It's pretty full-on at the moment." Does he think, whatever he does, he'll always be Gavin to them? "God, yeah."

If, at the ripe old age of 30, Horne is troubled by the thought that he may already have played his defining role, he's working jolly hard to ensure that's not the case. While 2008 saw his spectacular rise from Catherine Tate's sidekick (he played the unfortunate foil to both the belligerently sweary Nan and Lauren "Am I bovvered?" Cooper) to romantic heart-throb, 2009 is shaping up to be a year of wall-to-wall Horne (with a little Gavin on the side). First up is his West End debut, in Entertaining Mr Sloane opposite Imelda Staunton, rapidly followed by three major projects with his Gavin & Stacey co-star James Corden. Next month, the pair will present the Brit Awards with Kylie Minogue. In March, their new sketch show, Horne & Corden, comes to BBC3, and they star in Lesbian Vampire Killers, a Brit shlock horror flick that is being marketed as the next Shaun of the Dead. And there's still a third series of Gavin & Stacey to come.

Horne and Corden became best friends while playing best friends on Gavin & Stacey. As Gavin and Smithy, they have the kind of on-screen chemistry that only comes along once in a while, and the public can't seem to get enough of their particular brand of laddish camaraderie. But while Corden has, over the past few months, lived up to his on-screen alter ego, Smithy, risking over-exposure with his fondness for paparazzi-besieged nightspots, high-profile antics at awards ceremonies and an "are they, aren't they?" romance with Lily Allen, Horne has, in true Gavin style, hung back a little. They don't, says Horne, socialise very much (though they did spend 275 days of the past year together). "If you're talking in terms of fame and tabloid attention, I retreat more than James does," Horne admits. "And he embraces more than I do." Corden might have scooped the plaudits, the gossip-column inches and the magazine covers in the past year, but you wonder whether Horne might just be the tortoise who wins the race this year.

Entertaining Mr Sloane is an interesting first move. Joe Orton's notorious play in which a charismatic young man moves in with a dysfunctional family as a lodger, meting out sexual favours and sucker-punches to them in equal measure, horrified contemporary critics when it premiered in 1964. As Sloane, a slippery, sexually voracious psychopath dressed all in leather, Horne is sure to give Gavin devotees a shock. "A lot of the people who write letters to EastEnders characters who've murdered people saying, 'You're a bastard' are the same people who will say, 'Oh gawd, he's not Gavin. I want him to be Gavin again,'" Horne flaps his hands impatiently. "I'm an actor. Yes, it is a change. Gavin is a very straight, heterosexual, man's man who is a bit cheeky and who's got a heart of gold. But it wasn't a conscious decision to think, 'Right, I need to go and play a deviant, psychopathic murderer now.'" Which does he prefer playing? "I'm probably a bit more comfortable playing the latter," he laughs.

In fact, Horne has wanted to play Sloane for as long as he can remember, since first reading Orton at university a decade ago. In 2007, he met Kathy Burke when she came to play his mother (and Nan's daughter) on a Catherine Tate Christmas Special and the two became friends. They talked about his playing Sloane one day and, 18 months on, it has come together, with Burke acting as shadowy impresario or "artistic associate". It will, effectively, be Horne's professional theatre debut. "I didn't have any worry about whether I could do it technically. And I still don't," he says. "Whether I can do the part justice, I don't know."

So why risk it? "Over the last two years, my career has got to a point," he sits back on the sofa, "where I've just started to be able to make choices. Which really means I'm in the position where I can turn things down. That's the aim, really. It's very easy when you get yourself into that position to go and do things that will just earn you money. I didn't want to rest on my laurels of a couple of Baftas for Gavin & Stacey. I want to excite myself. The idea of me playing Mr Sloane in the West End was a dream 10 years ago."

Horne fell into doing drama at the University of Manchester 11 years ago. He realised early on – having been brought up on Laurel and Hardy and The Mary Whitehouse Experience – that comedy was what excited him most, a penchant which put him in the minority among his student peers, whose focus lay with "proper acting" and a future at Rada and the RSC. "I really struggled, deep down. That wasn't something that turned me on as an actor. Watching Steve Coogan live turned me on as an actor. But there was a certain snobbery about it – as if it was not really acting."

So – "and not a lot of people know this" – Horne turned down a three-year scholarship to the London Academy of Music and Dramatic Art (Lamda), and in his final year at Manchester started pounding the stand-up circuit, paying his way with the odd BBC Education video and commercial. He formed a double act with fellow student Bruce Mackinnon and they began to tour their sketch show, Mat and Mackinnon, around London and the Edinburgh Fringe. They were moderately successful, coming third behind Jimmy Carr in a Channel 4 competition and winning a few awards. When it became clear that they would progress no further, Mackinnon called it a day. I wonder how he feels now? "He's doing lots of stuff," says Horne. "He's a successful actor."

Horne went on, in the time it would have taken him to learn sword-fighting at Lamda, to star in Channel 4's 20 Things to Do before You're 30 and Teachers. Then Catherine Tate spotted him and gave him his big break. "I was hired to react," he says, pragmatically. "And, essentially, that's why I was hired on Gavin & Stacey, too." Does he mind always playing the straight man? "I don't think I'm funny as an actor," he shrugs. "I'm making other people funnier." I think he's being overly modest. When I ask whether anyone else was considered for the role of Gavin, he admits, shyly, that Corden told him it could only have been him.

He has his own theory for why Gavin & Stacey has been such a success. "It came at a time when on television there was a lot of darkness and black comedy and in society everybody was falling out of love and getting divorced. That show provided positivity, warmth and charm and two people falling in love absolutely and wholly." They're preparing to film a third – and probably final – series, but Horne sounds more than a little offhand at the prospect. "I don't think it will go on for ever. When something's done, it's done. It would be terrible to prolong it and for it to deteriorate."

He's much more animated talking about Horne & Corden, of which he is "immensely proud". His favourite character is Tim Goodall, a flamboyant cross between Dale Winton and Gok Wan, who becomes a BBC war correspondent, while Corden's is Xander, a braying ex-public-school boy who turns up at the most inappropriate times for his old school chum. "They're our Nan and Lauren," says Horne. There's also an extended riff on Superman and Spider-Man, "who both live in Crouch End, but don't know each other."

So what next? Does he have a list of people he'd like to work with? "Kathy Burke's been my mum. Catherine Tate's been my nan. Alison Steadman's been my mum. Imelda Staunton's now being my faux mum/lover. That's weird. I remember lying in bed, when I was at school, watching Nuts in May. Twelve years later, I'm Alison Steadman's son in a show which is winning awards. There are no words for that," he says. "I'm doing a West End play, I've got my sketch show coming out, I'm hosting the Brits. That's amazing. So, a list? I'm all right at the moment, really."

Entertaining Mr Sloane, to 11 April, Trafalgar Studios, London (0870 060 6632); 'Horne & Corden' starts on BBC3 in March; 'Lesbian Vampire Killers' is released on 20 March