Just for clarity, the peace sign in Britain still means peace, unless it's turned around to show the back of the hand, the same way Americans use the middle finger. Here's some quick photo references:
Ginger girl = fuck you
John Lennon = Peace
There's also the expression "put up two fingers to [blank]" meaning "told them to fuck off." Of course with American influence so widespread, the middle finger also works.
The story, supposedly, goes back to the British longbowman during the Hundred Years War. Captured bowmen would have their fingers cut off to prevent them from ever using a bow again. Those who had never been captured would taunt the French by raising two fingers as if to say "still got 'em."