Boys from the shop floor head for the red carpet

Only last year they were working in London clothes shops, selling suits and dresses.

Today an underground indie rock band called The Boxer Rebellion find themselves Hollywood celebrities, sharing red carpets and paparazzi flashes with Drew Barrymore.

They're still unsigned and have never troubled the singles charts, but that's set to change, now that The Boxer Rebellion are film stars. The band take a central role in Going the Distance, the big Warner Brothers release of the autumn, performing their own songs on stage with their name writ large on the backdrop and a packed audience screaming in appreciation. Not only that, Barrymore is depicted as one of their most ardent fans.

Her co-star Justin Long, who plays a record company A&R man, is shown excitedly logging in to the band's website and purchasing a CD at a gig. At a time when the music industry is financially stricken and record companies are playing every promotional trick in the book to raise the profile of their artists, The Boxer Rebellion have pulled off an unprecedented product placement deal without paying a penny.

Until early last year, lead singer Nathan Nicholson and bassist Adam Harrison had jobs at the London clothes shop Ted Baker, having previously worked in the shoe chain Office. "It was kind of embarrassing," said Nicholson. "There were a couple of times when I was serving customers and they would ask me, 'Are you in The Boxer Rebellion?'"

As they trod the red carpet at the world premiere of Going the Distance in London on Thursday, the band were swamped by autograph hunters, many of whom will not have known whose signatures they were collecting. On Monday, The Boxer Rebellion fly to Los Angeles for the US premiere.

The band was formed in 2001, shortly after Nicholson arrived in England from his native Tennessee. Harrison and drummer Piers Hewitt are British, and lead guitarist Todd Howe is Australian. They appeared at Glastonbury in 2003 and briefly signed to Alan McGee's Poptones label, which collapsed shortly after the release of their first album Exits. With the music business in decline their careers stagnated and they were obliged to make a living in retail. When they met their manager Sumit Bothra at the end of 2008, The Boxer Rebellion had another album of material but no cash to release it.

The band got a break when an iTunes executive, who had heard their ill-fated first album, offered to support the release of the second album, Union, as a download. It was popular enough for Bothra to persuade the band to "give up their day jobs" and hit the road.

Among the audience at The Boxer Rebellion's first US show, at The Troubadour in LA, was a group of film industry spotters looking for soundtrack material. They were so smitten that they advised the director Nanette Burstein, who was making Going the Distance, to attend a New York show. Impressed, Burstein invited the band to her Manhattan bar The Half-King, where she asked them if they would like to appear in the film. "At that time the script had a completely nondescript band that only appeared as a CD," said Bothra. The Boxer Rebellion were asked to contribute two tracks to the soundtrack, which is released on Monday.

The Boxer Rebellion were filmed performing "Evacuate" and "Spitting Fire" at the Southpaw club in Brooklyn, New York. A second gig, the climax of the movie, was filmed at the prestigious Bowery Ballroom in Manhattan, where they played "If You Run", written for the film. "The weirdest thing was that there was a room full of extras and they were going absolutely crazy," said Nicholson. "Then the director yells 'cut' and they go silent." The band will realise a dream on 23 September when they play the Bowery for real.

Although "If You Run" is the prelude to Barrymore and Long's characters being reunited, the previous draft of the script of Going the Distance left the two lovers in the limbo of a more ambiguous finale, for which the band made an alternative track, "Both Sides Are Even". But whatever the ending, this looks like just the happy beginning for The Boxer Rebellion.