Joanne Froggatt: From maid's outfit to army fatigues

If Joanne Froggatt has one complaint about Downton Abbey, it would be the frocks. Not that the costume department did anything wrong; it's just that, as head housemaid, her character, Anna, was somewhat limited in her wardrobe options. And the set was positively dripping with stunning Edwardian gowns.

The wounds are still raw when we meet in an overheated Soho office soon after the period blockbuster has finished airing. "Every day, I went, 'Ohhhhh. I've got such costume envy.' Every. Single. Day. I bet they were sick to death of me. I'd be like, 'Oh this is beautiful! Oh, look at the boots!' I was obsessed," she admits. "I kept saying, 'Can we not write a scene where Anna raids Lady Mary's wardrobe, or Lady Mary goes, 'Anna, just try what you want, just take it, honestly!' That was the only downside to it, not getting beautiful frocks."

With a second series due to start filming in February, there might be hope yet for Anna's sartorial longings, particularly if she cements her tentative love affair with Mr Bates, the lame valet played by Brendan Coyle. Even servants used to dress up to get married. Oh, and if Julian (soon to be Lord) Fellowes is reading, then Froggatt does have one more slight quibble: a speaking scene with Dame Maggie Smith, who plays the formidable Dowager Countess of Grantham, wouldn't have gone amiss. "Maybe next series," she adds, hopefully.

To be fair, she is plainly thrilled simply to have landed a part in the show, which has been the most successful period drama since Brideshead Revisited in 1981. In the intervening decades, the BBC has become better known for period drama, and it has taken people by surprise, says Froggatt, that the series was on ITV.

"I was really pleased, actually, because it goes to show that they can do it. There's almost a snobbery sometimes about ITV and period drama, because the BBC is so famous for it."

She's also pleased that it proves the viewing public has an appetite for something (slightly) weightier than endless reality TV shows. "I like X Factor as much as the next person, but I do get overwhelmed with the amount of reality TV. It's such cheap programming and such a load of rubbish, most of it. But people do like to watch good drama."

It's something of a year for Froggatt, who turned 30 in the summer. She arrives at our interview suitcase in hand, fresh off the train from Manchester, where she was filming The Royle Family Christmas special. She plays opposite Ralf Little as Anthony Royle's girlfriend, Saskia, who is expecting the couple's first child. The show pulled in more than 10 million viewers last year, making it the most watched of the festive period.

And next week, Froggatt's first feature film, In Our Name, is released in cinemas. As Suzy, a British soldier, she is fresh back from serving in Iraq. But settling into civvy street and, specifically, family life proves harder than she bargained for, with the guilt of an Iraqi child's death weighing heavily on her post-traumatic stressed mind. The role has won her a best newcomer nomination at next Sunday's British Independent Film Awards. (The film, by the first-time writer/director Brian Welsh, is up for another.)

She can barely contain her excitement at the prospect of her inaugural starring role at an awards do. But, first, there's the small matter of nailing a dress. "I'm so thrilled to be nominated for my first film; it's such an honour, so I'm really looking forward to the night, although I haven't got anything to wear yet."

Despite the success of Downton, Froggatt hasn't yet hit the big time, which means designers aren't quite beating a path to her door. A shopping trip beckons as soon as we're through, although, with time of the essence – she starts rehearsing a new play tomorrow – the ideal would be for someone to lend her something. She wore a borrowed Vivienne Westwood number for the premiere of In Our Name at the London Film Festival, so more of the same would be nice.

At least the whippet-thin Froggatt has size on her side when it comes to designers' samples. Like most actors, she is much tinier in the flesh than on the screen; her Downton corset can't have had much to pull in. For our interview, she is simply dressed, in a thin-knit black sweater dress with black tights and black over-the-knee flat suede boots. A patterned scarf breaks the monochrome, her spiral-tonged blonde hair lifting the ensemble.

It's a far cry from In Our Name, which sees an increasingly troubled Suzy stick mainly to army fatigues. It's not a glamorous role, although the low-budget debut proves you don't need bells and whistles to make an impact. The film is powerful stuff; an overdue airing for the pressing problem of how soldiers function after a brutal tour of duty. And particularly how women fare, given that the wars in Iraq and Afghanistan have seen them fight alongside men on the frontline for the first time.

It was only watching the premiere, with several friends in tow, that Froggatt realised quite what she'd pulled off. "Everyone thought, 'Wow, it's a really hard-hitting film.' I didn't realise how much of an edge-of-your-seat film it was until my friends said, 'Oh, my God!' People said, 'It's a really important film to see at the moment.' I think it is an issue that we are going to come across a lot more from now onwards. It's quite harrowing viewing at some points."

I can certainly vouch for it being traumatic. The luxury of watching a screener, meant I could – and did – pause the action when it all became too much. Not that that helped with the not entirely conclusive ending.

"[Brian Welsh] cut 10 minutes off the ending, which I think makes it so much better and stronger. Before, it tied up all the loose ends, but Brian felt that wasn't true to life, because one of the things with PTSD [post-traumatic stress disorder] is that it doesn't just go away and everything isn't just OK. There isn't a happy ending. People can suffer with this for the rest of their lives," she pauses, drawing breath.

"So it isn't a quick-fix problem, and I think he felt that tying up all the loose ends gave the film a movie-land happy ending rather than keeping the reality of it. That's what he's striven for all along. He wanted the audience to have a 'what next?' feeling. And to relate that to 'what's next for our soldiers and what can we do about it?'."

Even with the excitement of the film opening, the modest Froggatt, who is softly spoken with an even softer Yorkshire accent, isn't convinced that she's had her big break. "Maybe I'm still waiting for it. I suppose, possibly, at the moment things are going the best they've ever been, with Downton and a film, but, still, maybe it's not happened long enough for it to be a Big Break."

Her cinema debut is arguably overdue given that she's had the performing bug since she was a toddler. "My mum said she remembers me asking her if she'd take me to ballet lessons when I was about two and a half. She said I could barely speak and yet was asking for ballet lessons. She was like, 'Where the hell is she getting that from?'" Aged about seven, she cried after watching a Michael Jackson film at the cinema because it featured a little child that wasn't her. "I was neurotic and weird from an early age."

With no Froggatt acting dynasty to propel her theatrewards, it took a committed 12-year-old, begging her parents to send her to stage school, to launch her career. Three years at Redroofs, the Maidenhead theatre school, did the trick. Although she had hoped to go on to Rada, she landed an 18-month role as the teenage single mum Zoe on Coronation Street shortly after leaving.

"All you want from drama school is to be working afterwards, and I'd already got the work, so I thought it would be silly to break off, but sometimes I do think, 'Oh, I've missed out on a little bit of education there.' But I wouldn't change the ways things have gone."

Cutting her acting teeth on TV sets rather than theatre ones means she is nervous about starting work tomorrow, for a lead in The Knowledge, a new play about a young teacher at the Bush Theatre in west London.

The job has the advantage of being commutable from High Wycombe, where the born-and-bred Northerner lives with her partner, James, who runs an IT company. She picked him up in a bar (really) in Beaconsfield, although she blushes to tell the tale. Unlike the black cabbie who pulled up in the street the other day to say he was "loving Sunday nights", the future "love of her life" (her words) hadn't tried to pull her because he recognised her.

If Froggatt lands any more prime-time roles, she had better get used to being stopped. Maybe then those fancy frocks will start falling into her lap.

Curriculum vitae

1980 Born 23 August, in Scarborough, North Yorkshire. Has one brother, Daniel, four years older. Aged four, her parents buy a smallholding to live the "good life" and she is brought up on a 10-acre farm near Whitby, where she attends Sleights School.

1994 Convinces her parents to send her to Berkshire's Redroofs theatre school. Gets her first acting job as a teenage prostitute in The Bill two years later.

1997 Leaves Redroofs and does a stint at WH Smith before landing a job on Coronation Street as Zoe Tattersall, a teenage mum, which lasts 18 months. Abandons plans to go to Rada.

1999 Has roles in Bad Girls, Dinnerladies, Lorna Doone and A Touch of Frost before being cast in the starring role in Danielle Cable: Eyewitness five years later, earning herself a Royal Television Society best actress nomination.

2007 She plays Joanne Lees in Murder in the Outback, a drama about the suspicious death of the backpacker Peter Falconio.

2010 Appears in ITV's Downton Abbey and In Our Name, her first feature film.