Hallam Foe won the grand jury prize, the Golden Hitchcock, at the 18th Festival Du Film Britannique in Dinard, France.
David Mackenzie's feature, based on the novel by Peter Jinks and starring Jamie Bell, has previously screened in Berlin, Cannes and Edinburgh. It was released in the UK on August 15. The Dinard prize comes with $4,400 (Euros 3,100) towards French distribution and a $2,100 (Euros 1,500) grant to the director.
The film was also awarded the Kodak Limited Prize for best director of photography.
The Premiere Prize audience award went to Sarah Gavron's Brick Lane, based on the novel by Monica Ali. It also won the Grand Mariner trophy for best screenplay, written by Laura Jones and Abi Morgan.
Garage, directed by Lenny Abrahamson, won the Heartbeat prize, which supports distribution in around 40 cinemas in Brittany.
This year's jury included Sylvie Testud, Imelda Stauton, Linh Dan Pham, Michael Grigsby, Kerry Fox, Cecile Cassel, Etienne Chicot, Jocelyn Quivrin and Laurent Gerra.
Additional films in competition at the festival were Julian Jarrold's Becoming Jane, Asif Kapadia's Far North, Mark Jenkin's The Midnight Drives.
John Carney's Once was also in competition and received a special mention from the jury at the awards ceremony.
Other films screened at the festival include Joe Wright's Atonement, Marc Munden's The Mark Of Cain, Anand Tucker's And When Did You Last See Your Father' and Jan Dunn's Ruby Blue.
Attendees included directors Oliver Parker and Tom Collins and actors Glen Hansard and Gerard Kearns. Shane Meadows and his producer Mark Herbert were also in Dinard for a retrospective.
The British Film Festival in Dinard is supported by the UK Film Council, The British Council and France's CNC.