DanteFox said:prove me wrong. (You can't use depp because I already took him into account)
Peter Sarsgaard in An Education:
http://www.youtube.com/watch?v=qn9IMe5jmf0
Him in an interview:
http://www.youtube.com/watch?v=LfElzPWlYrU
I was surprised to hear his actual accent. I can't vouch for the accuracy of his British accent, though.