The British soldiers all stood in a line and only fired their gun on demand. Because of this and the fact that they wore bright red colors they were easy to spot in the forest.
The French had a very different fighting style than the Brtish. They camoflauged themselves and used the environment to their advantage. They hid in trees and bushes to surprise the British.
Because the French were hidden the British soldiers did not know where the bullets where coming from so they did not know how to defend themselves. But the British were great in numbers which was helpful for them.