Joanna Page: Back on a winning streak

"Is there anything else you'd like to ask me? Because I can just talk", says Gavin & Stacey actress Joanna Page near the end of our interview, and she's not kidding.

Small, blonde and irrepressible – her sentences a torrent of lovely sing-song Welshness, with longer words cleaved neatly down the middle (“mil-lion”, “act-ress”), Page is Stacey.

It was a truth immediately apparent to her character's creator, Ruth Jones, when she bumped into the actress in the toilets while casting the hit BBC sitcom. "We got talking," recalls Page, "and apparently Ruth went back into the auditions and said, 'I've just met Stacey'..."

It's now well over two years since the last episode of Gavin & Stacey, and while Ruth Jones has gone on to pen her own starring vehicle, the successful Sky1 sitcom, Stella, and James Corden seems to have popped up everywhere, from Doctor Who to hosting the Brit Awards, by way of the West End stage – it wouldn't be unfair to suggest that Page has strayed a little way off the radar.

Yes, she's the face of Superdrug, presents a Sky1 show called My Pet Shame and voices a pre-school animation, Poppy Cat, but she has been largely absent from our screen dramas of late, although that is all about to change.

In BBC1's upcoming The Syndicate, written by Kay Mellor she is among a group of supermarket workers who win the lottery, while in September she plays one of the parents thrown together by their children's choice of school friends in Sky1's The Gates. And then at Christmas, she'll be appearing as David Tennant's husband in Nativity 2. In each of the series she plays a mother – a graduation that many actresses fear, but which Page welcomes.

"For so long I looked so young for my age that it's been quite frustrating because in my thirties I was still playing 17-year-olds", she says. "Now I'm really enjoying playing mothers... it just feels a bit more grown up. I'm hoping I can start playing policewomen soon".

Gavin & Stacey is one of those runaway hits that either make or break an actor – and having recently read Susannah Corbett's biography of her father, Harry H Corbett, a highly regarded straight actor who forever became identified with Harold Steptoe in Steptoe & Son, I asked Page about the perils of typecasting. "I never panic about typecasting," she replies. "Even if it asks for 'a bubbly blonde Welsh girl', if I like the script I'll go and meet for it. What was really strange was that friends were telling me that they were going up for auditions and the casting thing would say 'Joanna Page type' and I'd think 'why don't they just phone me and ask 'would you like the part?'

"Some people assume that I'm a stand-up comedian – I couldn't think of anything worse – and then they ask 'would you like to do something like a costume drama?'... 'would you like to do something more serious?' And I think 'good God, Gavin & Stacey is literally the only comedy that I've done. And also I don't think that Stacey is a comedy character... I don't think about being funny, I just say the lines as they are."

As Page points out, she had been in the business for nearly a decade between leaving Rada in 1998 and first playing Stacey in 2007, with film roles in From Hell and Love Actually to TV dramas such as The Cazalets and Making Waves. There was one low moment when she did consider giving it all up to try and become, of all things, a criminal psychologist. "I actually got around to applying to the Open University," she says. "And then the script came in for Gavin & Stacey, and it was the only thing I'd read in absolutely ages that I loved and I thought if I don't get the part that's it – I'll finish it".

The Swansea-born actress was, along with Sally Hawkins, the student in her year at Rada that her contemporaries thought had the brightest career ahead of her. That, at least, is what Page's good friend and classmate, Maxine Peake, told me when I interviewed her recently. Page remembers it all rather differently. "Oh, my God, no, not at all," she says. "I remember devouring Kenneth Branagh's autobiography before going and thinking it's going to be amazing and it wasn't. It was awful.

"I was so, so homesick, and I'm a very instinctive actress, I'm not technical, and everything had to be Method and they wanted to strip everything away from you. I just spent most of the time being told to lose my Welsh accent, to speak in RP accent all the time... and my acting teacher saying to me 'you're rubbish, you're shit, there's nothing I can do with you'. It was just unbearable and I left early.

"I just remember looking at the girls who were so English and they were all called Pippa and Candida and I desperately wanted to be like them, but I was a sweet, innocent and slightly rough Welsh girl."

Ironically, her future husband, actor James Thornton, thought she was a Pippa or a Candida and that "he'd never have a chance with me because he's very rough and Northern and he thought I wouldn't even look twice at him". The couple had both been in the 1999 costume drama David Copperfield but never met during filming, becoming mutually smitten when they saw each other on TV.

"There was this scene with Daniel Radcliffe, who played David Copperfield," she recalls, "and James lifted Daniel up and put him on his shoulders and I remember turning to my mum and saying 'I want that man to be the father of my children'." It was her friend, Maxine Peake, who engineered the eventual meeting. "Maxine phoned me one night and she was in The Cherry Orchard at the National and she said 'there's a man here and he says he's in love with you, so will you come and watch the show? His name's James Thornton'. I met him afterwards and that was it."

The couple married in 2003 and are in the process of moving to "a lovely little thatched cottage in Oxfordshire", and indeed Page's dream – should she ever win £4 million on the lottery, like her character in The Syndicate – would be "to get more animals (she already has a Jack Russell called Daisy), have some land, and then buy myself a little boat and just be on the boat with James up and down the Thames".

James recently ended a three-year-stint on the ITV soap Emmerdale in fairly terminal fashion by driving his character's car over a cliff. "When he first went into Emmerdale I started to watch, but I got bored then and stopped watching," says Page, understandably. "When he died, I thought 'well, he's not dead he's sitting here beside me on the sofa'." Stacey herself couldn't have put it better.

'The Syndicate' begins tomorrow at 9pm on BBC1