Cardiff confidential: Saying farewell to Gavin & Stacey

Just 24 months ago, the first series of Gavin & Stacey had finished airing on BBC3, attracting a respectable but hardly earth-shattering half a million viewers and a few approving reviews.

Telling of the love affair between Welsh girl Stacey (played by Joanna Page) and Essex boy Gavin (Mathew Horne), admirers enjoyed its good-natured culture-clash scenario, the tenderness towards its characters and the freshness of the actors (who also included the show's creators, Ruth Jones and James Corden, as the lovebirds' best friends, Nessa and Smithy).

Two years on, and Gavin & Stacey has won two Baftas and countless British Comedy Awards, seen its audience triple for the second series and, in 2008, mushroom even more exponentially for a BBC1 Christmas special. The third series begins next week and once again Jones's and Corden's creation is being given the honour of premiering on the BBC's most popular channel. We've seen our heroes fall in love, marry, co-exist with the in-laws and adapt to the culture gap between Billericay in Essex and Barry Island in South Wales. Where can it go from here? And can it retain its endearing joie de vivre?

The most obvious novelty is that, with Gavin starting his new job in Cardiff, the action has shifted to Wales, which means that Mathew Horne has to wear the homesick, fish-out-of-water expressions this time around. "We meet some new characters this time too," says James Corden. "But the core of the show is essentially the same." So what has held Gavin & Stacey in such widespread affection?

"It's amiable, unpretentious, well-scripted, nicely acted and archly amusing," wrote this newspaper, reviewing the still fledgling show. "It's a good series, taking its place in a well-worn comedic progression, stretching back to The Liver Birds." In fact, Gavin & Stacey seems so out of sync with the vogue for TV comedy about TV people – from Larry Sanders to Larry David, by way of 30 Rock and Extras – that it almost seems radical. Ordinary people living ordinary lives? Man, you should see this.

Not everybody was seduced, however, and once the awards started flooding in, they were swiftly pursued by an inevitable backlash. It's quite nice, but it shouldn't get above itself, was the general tone of the caveats. One broadsheet critic went further and called Gavin & Stacey "predictable, old-fashioned and wearing... it feels like a first draft, with no polish or aplomb to it. And now, to top it all, it's overrated too" – an attack that was squarely batted back by co-creator Ruth Jones. "It gets lots of criticism levelled at it for being too sweet," she said. "But I think that's why people are so fond of it, because it's not cynical or edgy. James and I really love the characters and we're so pleased that everybody else shares that."

But can Gavin & Stacey be entirely sweet and innocent when it calls its two leading families the Shipmans and the Wests – and a supporting character Peter Sutcliffe? This taste for mass murderers aside, Gavin's father, Michael Shipman, is played by Albert Square's Mr Evil, Larry Lamb (Archie Mitchell in EastEnders), while Gavin's doting mother is played by Alison Steadman. Along with Rob Brydon and (as Nessa's mother in the new series) Pam Ferris, there is someone for everyone.

Indeed, Gavin & Stacey has all the ingredients for it to become an audience-pleasing family sitcom in the tradition of Only Fools And Horses and The Royle Family – churning out series after series and Christmas special after Christmas special – everything, that is, except the willingness of its creators and writers to carry on. For the third series of Gavin & Stacey is also its last.

"There will never be another series of the show," confirms Corden. "I think Ruth and I are definite about that. As far as specials are concerned, I think if we had an idea for a story with these characters then maybe, but I don't think that'll happen any time soon."

"Where would we go with it?" asks Jones, and viewing the opening episode of the new series, it's hard to disagree with her. If I hadn't watched it in the knowledge that this sitcom's existence was finite, I might have feared that it was drifting into a comedy half-life of contrived plots and stagnant characterisation. "No, it's really time to say goodbye to these characters now," says Jones. "James and I will definitely write together again, though – we want to write a film." A Gavin & Stacey film? "No, because G&S very much belongs to the little screen, not the big one."

Just because saying goodbye to these characters is the right thing to do, it doesn't mean that it was easy. "In the final week me and Jo Page just couldn't stop crying," says Jones. "We were pathetic and we looked like frogs. And on the last day me and James were awash. It sounds silly, I know, but it's been a big part of our lives for the past three years... But, y'know, things have to move on."

For Jones and Corden, that means further script collaborations. Meanwhile, the end of the current series won't entirely spell the end because the show is to be remade for US television. NBC originally planned to make an adapted American version with Gavin coming from New Jersey and Stacey from South Carolina, but now ABC has bought the rights.

"It (the NBC script) wasn't great, to be honest," says Jones. "But now ABC is looking into writing a pilot and hopefully that will work out. I think we got £2,500 for signing over the rights. We'd only make loads of money if it runs for five series and became syndicated. The only thing that has managed that is The Office, so ... we're not millionaires yet."

Gavin & Stacey is on BBC1, Thursday at 9pm