IT'S tough being a movie star.

Learning lines, waiting around on set, having your Saturday night sleepover interrupted by a journalist's call. Happily, Eloise Laurence, 13, is as cool with this as she is in the new British drama, Broken.

"We've got the pizza and everything," she reports when asked how the night is going.

In Broken, Laurence plays Skunk, a girl caught in a world of warring neighbours in a suburban cul-de-sac. While the film also features Tim Roth (Reservoir Dogs) and Cillian Murphy (Inception) it is the outstanding performances of the young actors, among them Laurence and Robert Emms, that have made the picture such a hit at film festivals from Glasgow to Cannes. Adapted from the novel by Daniel Clay and directed by Rufus Norris, Broken goes on general release next week.

When it came to working with the likes of Oscar-nominated Roth and Murphy, age gave Laurence an advantage.

"I hadn't heard of them before," she says. "It was best that way because I think if I had heard of them I would have acted completely different around them, and we wouldn't have had the bond that we have now."

Emms, 26, plays Rick, a young man who, save for his friendship with Skunk, has trouble connecting with the world. As much a student of British drama as any young actor, Emms was well aware of his co-stars' cvs. He says he learned a lot from them, Roth in particular.

"The most amazing thing was watching how they form relationships with other people on set, how that informs their performance, especially Tim with the kids," he says, speaking on a visit to Glasgow for Broken's film festival screening.

However, the most important lesson came from Laurence: "You look at children when they are acting and they sort of take away all the stuff that adults put on there."

Broken was Laurence's first proper acting job. Her last gig before that was a school production of Little Shop of Horrors. "It was a massive step up from primary school productions to a main character in a film," she says.

For Emms, Broken is the latest stop in a career that has gone from the stage production of War Horse to appearing in the Steven Spielberg-directed film. Add to this parts in Anonymous, Mirror Mirror (with Julia Roberts), The Arbor and the forthcoming Kick-Ass 2, and it is clear why he was named one of Screen International's "stars of tomorrow".

Not that his career started all that smoothly. Emms, from Surrey, was born Robert MacPherson, proud grandson of a Highlands grandfather. His aunt, uncle and cousins live in Kirkcaldy. With all this background, and many a holiday spent here, he was keen to keep the family name. Unfortunately, so was another Robert MacPherson, who had registered it with Spotlight, the casting directory, one week earlier. So, taking the first letter from his Scottish surname, MacPherson became Emms.

His big break after leaving the London Academy of Music and Dramatic Art in 2007 was being cast in War Horse – particularly when Steven Spielberg decided to catch the play on a visit to London. The cast knew there was going to be a film, says Emms, and were aware the Oscar-winning director was in the audience.

"Everyone was shouting quite a lot," laughs Emms, recalling that night's performance.

Spielberg spoke to him afterwards. "He asked whether I had ever done any films, whether I had thought about it. He dropped all these hints. I didn't think anything of it, then I got a phone call to say he wanted me to be in the film." In the screen version, he played the spoiled son of a rich landowner, which made a change after hundreds of performances playing the kindly Albert on stage.

Being in a Spielberg blockbuster was an eye-opener. The sheer size of the production, from the sets to the lights to the catering, staggered him. However, Spielberg took the time to make sure the young actors did not become lost in the fray.

"He's very aware that he is detached from everything in a way," says Emms, "so there were lunches before shooting started and rehearsals. On set he gave us time just with him. He's aware of creating that intimacy because he understands the set is so big it can create a distance between people."

Emms will be seen next in Kick-Ass 2, the follow-up to the crime-fighting comedy adapted from Mark Millar's comic book. Emms plays Insect Man, one of a group of not-so-super superheroes: "He's a guy who has an obsession with Spider-Man."

Although the character doesn't have anything in the way of superpowers, Emms was given truncheons – and has the scars to prove it. "I needed a plaster," he laughs, pointing out the place between his thumb and index finger where the chafing took place.

Among his co-stars in Kick-Ass 2 is Jim Carrey. "He was nice. Really mad. He's great at improvisation and made it a fun experience for us all."

Having made her mark in Broken, Laurence, from London, will wait until she is older before deciding what she wants to do next. She is also a keen musician.

"I've just taught myself guitar. I sing and write songs, and that's my main passion," she says. "I do love acting but if I had to choose between them, music would be the one for me."

Until any decisions have to be made, she's happy to go back to being an ordinary teenager, sleepovers and all.

Broken opens on March 8