Grandmaster Yip Man did not actually fight any British boxing champion. In real life, it was actually Yip Man's student, Wong Shun Leung ("Wong Leung" in the movie), who fought a 240 lbs Russian (not British) boxer in Hong Kong.

Who defeated Ip Man?

At age 16, Ip Man moved to Hong Kong, where one could say a little twist of fate occurred. Ip Man is said to have met a man named Leung Bik, who requested a friendly sparring match with Ip Man. Leung Bik soundly defeated Ip Man, but he highly praised Ip Man's Kung Fu abilities.

Did Ip Man really fight General Miura?

He in fact did fight a General Miura in a small tournament, was in fact shot and as proof he became an Opium addict because he has used Opium to help ease the pain of his gun shot wound during that time but eventually became an addict of it.