Ealing Studios' resurrection of the popular 1950s and 1960s St Trinian's film franchise is proving to be one of the shining lights at the UK box office.

The schoolgirl comedy, based on the cartoons by Ronald Searle, had a budget of $13m (£6.5m) and has taken $24.8m (£12.3m) at the UK box office alone. It has also sold to a number of territories where it has yet to open, including Italy, Germany, France and Scandinavia.

Barnaby Thompson, head of Ealing Studios, who produced and co-directed the film alongside Oliver Parker, suggests success is largely down to the support and guaranteed distribution deal with Entertainment Film Distributors. 'Entertainment was very supportive,' says Thompson. 'Without that, the numbers wouldn't have added up.

'The challenge with the film was that, in order for it to compete, it had to be made on a big scale. We were very ambitious in terms of the production values and the casting. And the fact that it's a concept that is very UK-centred made it difficult. It had to have a budget that was big enough but also achievable in the UK.'

The film generated early buzz during production through announcements of key cast members, including Colin Firth, Rupert Everett, Stephen Fry and Lena Headey.

In addition to these British favourites, young girls - the film's target audience - were lured by additional popular cast members such as British comedian Russell Brand (about to hit US cinemas in Judd Apatow's Forgetting Sarah Marshall), US TV star Mischa Barton, model Lily Cole and pop group Girls Aloud.

'As we were shooting the film we were getting a lot of press, which was generating good, early buzz,' says Thompson. 'We were originally going to release the film at Easter 2008 but based on that good buzz, Entertainment moved the film up to a Christmas release.

There was an opportunity here as it is aimed at a kids and family audience but it was still a bold move because we were then up against the Hollywood biggies.'

The film also succeeded by targeting a niche audience - young girls aged 10-16 - who have typically been underserved in the UK market, adds Thompson. 'For them to see other girls up on screen leading the story was something they found thrilling that they could relate to.'

Plans for a sequel are in the works. Piers Ashworth and Nick Moorcroft are writing the script.