Sexy Beast, starring Ray Winstone, is set in Spain
The film won best film, best screenplay, best director for Jonathan Glazer and best actor for Ben Kingsley.
Bifa founder Elliot Grove paid tribute to the films nominated, pointing out that this was a particularly good year for independent movies.
"We are delighted with the calibre of films this year," he said.
"The growing number of nominees and winners only proves that the British film industry is alive and kicking."
Sexy Beast, which has been a critical and box office hit tells the story of a retired gangster (played by Ray Winstone) pressed into service by various dubious figures from his past, played by Kingsley and Ian McShane.
Glazer, a first-time feature film-maker, is best known for his striking TV advertisements including the Guinness white horse commercial.
Winstone had also received a best actor nomination, but was pipped by his co-star.
The film fought off competition from Ken Loach's story of the California janitor's strike, Bread and Roses, high-octane drugs romp South West Nine and Jump Tomorrow to take the best film title.
Sexy Beast's producer Jeremy Thomas also won a special jury prize for best British producer.
The Bifa awards honour the best home-grown film-making talent, including trophies for best film, actor, actress, newcomer and director.
South West Nine, from the makers of hit film Human Traffic, won the new category for best music.
The soundtrack features Jamelia, Baby Fox and a unique collaboration, specially composed for the film, by Orbital and Alabama 3.
Other winners include Memento, starring Guy Pearce and directed by Christopher Nolan, which won the best foreign film in English.
Wong Kar Wei's In The Mood For Love, which was set in Hong Kong and has been compared to Brief Encounter, won best foreign film in another language.
And Kate Ashfield, star of Late Night Shopping, beat off strong competition from Kate Winslet in Enigma and Samantha Morton in Pandaemonium to win best actress.
Special prize
The shortlist was drawn up by a jury of 10, made up of key industry players including Primary Colours actor Adrian Lester, High Fidelity director Stephen Frears and the director of the BBC film Last Resort, Pawel Pawilowski.
They also gave out two special jury awards, as well as the jury prize for best producer.
British cinematographer Chris Menges, who worked on The Pledge, The Killing Fields, The Mission and Michael Collins won the lifetime achievement award.
A special prize went to Bob and Harvey Weinstein, the co-founders of Miramax films, who have executive produced films including the forthcoming Lord of the Rings trilogy, as well as Chocolat, The Others and Spy Kids.
The Variety UK personality of the year went to Richard Curtis, who wrote the screenplay for Bridget Jones's Diary and organises Comic Relief.
To be eligible for consideration, films must not be solely funded by a single studio.
They must also be produced, or majority co-produced by a British company, or in receipt of at least 51% of their budget from a British source.