Leonardo DiCaprio missed out on the actor of the year award at the 36th London Critics' Circle Film Awards as British veteran Tom Courtenay took the honour.
George Miller's post-apocalyptic thriller Mad Max: Fury Road was named film of the year, while Miller received the director of the year award.
The film's star, Tom Hardy, was named British/Irish actor of the year for his work in 2015 including The Revenant, and for starring as the Kray twins in Legend.
British drama 45 Years equalled Mad Max's tally of three awards, including British/Irish film of the year. Oscar nominee Charlotte Rampling was named actress of the year, while her 45 Years co-star Courtenay took home the actor of the year prize.
Winslet, 40, was named supporting actress of the year for her role in Steve Jobs, the biopic about Apple's co-founder. Mark Rylance received the supporting actor honour for Steven Spielberg's Bridge Of Spies.
Asif Kapadia's film Amy - which depicted the troubled life of the late singer Amy Winehouse - was named documentary of the year.
Brooklyn star Saoirse Ronan, who is nominated for the Best Actress Oscar for her role, was named British/Irish actress of the year.
Organisers extended the British categories at this year's awards to include Irish talent, with Ronan, Colin Farrell and Michael Fassbender among the nominees.
Game Of Thrones star Maisie Williams, 18, accepted the young British/Irish performer award for her lead role in The Falling.
Oscar nominee Benjamin Cleary claimed the inaugural British/Irish short film of the year award for his unconventional love story Stutterer.