Why were the French character's speaking English?

Because it is a British made film.

B/c it's made for an English audience so we're supposed to imagine that they're speaking French but we understand everything perfectly. It's just implied that they are really speaking French but what we hear is English...if that makes sense?

Because Germans are evil, so much so that whenever they speak, we have to READ SUB-TITLES so we know what they are saying!!!