Hannah Arterton and I are playing a game of Snog Marry Avoid?

A 1980s version for reasons that will become apparent in a moment. Your options are the following, I tell her: Simon Le Bon, Morrissey, George Michael, Madonna.

She wrinkles her nose as she thinks. "I think I would snog … Simon Le Bon, because he was hot. Still is, in a way. I would marry George Michael. That could work. We could be married and live separate lives and I would avoid … none of them. They're all great."

Arterton - actor, singer, youngster - was born on January 26, 1989 in Kent. So she was alive for all of one year and five days of the 1980s. You might argue, then, she's not the best judge of who was snoggable or not back then. But to be fair to her she does sing in a covers band called The Hitman And Her and they're always delving into the 1980s songbook. "Everyone loves a bit of Whitney," Arteron points out.

And, oh yes, she's got this new film coming out called Walking On Sunshine (based on the Katrina And The Waves track, not the Rockers Revenge version, unfortunately). It's essentially Mamma Mia! or perhaps Sunshine On Leith but, umm, eightier. So instead of ABBA songs and the Greek islands, the cast sing Huey Lewis, Madonna and Cyndi Lauper tunes around Puglia in Italy. It looks like fun, I tell her, though personally I could have done with a couple of Smiths songs in there. "I don't know if the Smiths would have allowed us," she laughs. "I think Morrissey might have been: 'A joyous summer film? No.'"

The other difference between Walking On Sunshine and Mamma Mia! is that the cast aren't quite as A-list as Meryl Streep and Julie Walters. It's more singer Leona Lewis and comedian and writer Katy Brand. But on the upside Greg Wise can sing rather more mellifulously than Pierce Brosnan. And Arterton gets a lead - her first. "Even if I never make another film, I played the lead in a big glittery film and it was fantastic."

It's a good fit for her. If her presence this London afternoon is anything to go by, sunny is her default position. But - as we'll see later - she's not been artificially sweetened. It takes grit to make a pearl.

Does she look familiar, by the way? Around the eyes and about the surname perhaps? Well, she should. She's Gemma's younger sister. Fresh milk to big sister's americano. Unlike Gemma, Hannah is new to the game. She has an appearance in Midsomer Murders and a role as a slave girl in the BBC Saturday-night drama Atlantis to her name and that's more or less it. So you're forgiven if you haven't noticed her before.

But that's about to change. Even before Walking On Sunshine opens in cinemas she's got a movie at this year's Edinburgh International Film Festival. Hide And Seek is an indie movie (maybe it will have a Smiths song) about partner swapping in an English country house. Well, I'm not an expert but maybe that's all there is to do after you've polished the cutlery. As it's the film's world premiere she's making the effort to head north. She's been here before. "Edinburgh is beautiful. I remember getting off the train and thinking: 'This place is just knockout.' I was like: 'Maybe I should move up here.'"

She doesn't know the second city quite as well. But, she says, "I'd love to have a good dirty night out in Glasgow." That means something different these days, right? Oh, these young people.

Arterton comes from the other end of Britain. She lives in Greenwich and grew up in Gravesend - where Pocahontas is buried, she reminds me - with her mother and her sister before any of them were famous.

There were no country houses in their story, it should be said. Her mother still lives in the council house they grew up in. Ask her for a first memory and she talks hand-me-downs.

"We weren't in poverty but things were quite tight. Single-parent family, my mum bringing us up. I remember my mum's friend had a daughter who was a couple of years older than me and so she'd give me her jumpers and stuff when she outgrew them. I had one jumper that was purple and had white ducks on it and I remember my mum putting it on me and it smelling so strongly of a different house. And me being like: 'Why do I have to wear this?'"

Her father Barry left when Arterton was three, though she saw him every weekend. Still, for a model of adulthood she could have done a lot worse than her mother Sally Anne. "My mum worked three jobs, was endlessly creative in her efforts to bring us up. She was amazing but she was never pushy, never demanding. She's a bit of a hippy and let us do our own thing and we naturally gravitated towards the arts and performance."

Arterton's role in the family was to be the baby. It still is, she says. "I'm striving to say I'm a 25-year-old woman. I'm not a baby." Even so, she likes the affection. You do wonder if big sister ever moaned about little sister copying her by expressing an interest in acting. I tell her copying is the biggest crime you can be accused of in my house. "No, not at all. I think she encouraged me."

Then again, their goals were a little different for most of their teenage years. In truth, Arterton wanted to be a pop star. "I wanted to be Gwen Stefani. I wanted to be in a band and do a world tour and have an album out." She's been singing in bands since she was 14. Cover bands, functions bands. "And then when I was 17 I realised the music industry is quite terrifying and difficult to navigate."

How so? "I had a manager and he did a runner. Luckily there were no contracts. There was no money involved. I just felt a little abandoned. In the acting world there's an infrastructure you can rely on. The music industry seems a lot more: '… Hi, I'm Dave. Come along with me …' 'Okaaay, you're wearing a nice suit, you must be Simon Cowell's brother.'"

She left music college without a band or a record deal ("which had been the plan"), did a musical at college to fill the time and the directors told her she should audition for drama school. "It was either that or work in a shoe shop." She auditioned for the Royal Academy of Dramatic Art and - to her amazement - got in. After leaving Rada she walked straight into a part at the Almeida theatre in London.

"I thought: 'Sweet, I'm set. First job. This is great.' And then didn't work for 10 months. Auditioned tirelessly and wasn't getting anywhere. I was working in bars, working until three in the morning every night just so I could keep my days free in case an audition came up. Living this weird double life. Having no money, getting into debt, really feeling 'this is so hard'.

"It's hard not to take it personally when you have 80 auditions and you don't get one job. You think it's because I'm fat, it's because I'm ugly, it's because I'm not good enough. And it isn't any of those things. It's just that you're a new actor and you've got to work your way up the ladder, like any job. But it's really hard when it's your face and your voice and your body being judged. It is your work but you cannot detach yourself from your physical state.

"I found that very hard to deal with at first. It is worth it. You just have to keep strong. Every audition where it doesn't happen, you just have to let it go or it will eat away at you. It's tough."

Oh, we seem to have somehow waded into deeper waters. You might argue, I suggest, that acting isn't the ideal career choice if you are uncomfortable in your own skin. The screen inevitably objectifies. "That's part of the job," she agrees. "Every actor knows that."

The thing is, Arterton is pretty and petite and should have no reasons not to look in the mirror. Plus, she's young. "That helps. But everybody has insecurities. Everyone. I know that even Kate Moss will have insecurities. For me, it is not productive to look into the mirror and tear myself apart. It's not going to help me achieve the things I want to achieve because it's just going to make me feel negative. I can't work unless I'm completely relaxed, so yeah, it's not productive for me to do that.

"Now I'm coming to a place where people are wanting to look at me and take my picture, which is quite a new thing. And I don't want to be a woman in the public eye who hates her body and hates her face and wants to look like someone else. I don't think that's a good thing for a woman. I think I quite like the way I look most of the time … some of the time."

On the upside, I point out, the only people being objectified in Walking On Sunshine are the male cast, in particular Giulio Berruti, Arterton's onscreen amour. "Yeah, I loved that about it."

Another 1980s interlude. Margaret Thatcher, Ronald Reagan, Tony Benn; which would you vote for, Hannah? "Tony Benn. Definitely. Without a shadow of a doubt." Can you name the stars of The Breakfast Club? "I don't think I can. That's dreadful." Dynasty, Dallas, Brookside or EastEnders? "I love Dallas but I'd have to choose EastEnders. The Phil Mitchell/Sharon storyline was huge in our house." Which is the greatest 1980s fashion faux pas: big shoulder pads, leggings or Tacchini track suits? "What were they? Shell suits? I can't bear the sound. Shussh, shussh, shussh. I quite enjoy a shoulderpad. It's quite a powerful feeling. And I wear leggings. They're very comfortable."

Maybe it's time to talk about Big Sister. Gemma Arterton is three years older than her sister and has Hollywood blockbusters, Britcoms and a Bond movie on her CV. Her sister is a little in awe of her. "I feel like she's more of an inspiration than an influence. She has achieved such an incredible amount in such a short space of time. And we came from quite a humble working-class background. To then be soaring into this world that can be quite elite, that's quite difficult to get into if you haven't got the money. Being an actor without an independent financial resource is quite difficult." Gemma, she says, has made it look easy.

"I remember when she got the Bond movie and then Prince Of Persia, my friend Lauren from home, who's an artist, said: 'This is so brilliant. A girl from our town can do these incredible, world-scale projects. It's possible.'

"Whether it's acting or whether you want to be the head of a bank, knowing there's no limit if you've got enough drive to what you can achieve … People from a working-class background, I feel, are frightened to go and do it because they don't think it's possible. But I think Gemma has proven that it is if you work hard enough and are fearless."

It maybe helps to have wealthy parents, though. We now live in a world of public school-educated Dominic Wests and Benedict Cumberbatchs. "I don't think their backgrounds have anything to do with how talented they are. They're fantastically talented," Arterton says. Agreed, but the question is, outwith the soaps, is the working-class actor disappearing? "It is hard. It is hard to be out of work and keep the faith when you're approaching 30 and working in a bar. You have to simultaneously keep things ticking over in the real world to earn money. You feel you are constantly starting over all the time. It's hard when you're in and out, temping or working in a shop. For me, I try to see the positive in everything. That will keep me a real person and give me - not that I ever will forget - a constant reminder of how it is to live in this world. Because sometimes actors can be out in this other place, this weird Actorland."

What does Actorland look like, Hannah? "It's very beautiful. Lots of fluffy clouds. Lots of beautiful dresses."

Anyway, she says, in the end the great thing about being an actor is that class doesn't matter on the screen or on stage. "That's something I love about this job. Next I could play a queen. How fabulous. I grew up on a council estate and I'm playing the Queen of France."

Casting directors looking for a new Marie Antoinette start here. n

The world premiere of Hide And Seek at the EIFF takes place next Friday in Cineworld, Fountainbridge at 6.15pm. There will be another screening on June 22 at 1.30pm. Visit edfilmfest.org.uk. Walking On Sunshine (12A) goes on general release on June 27.