Just to clarify the law for foreign residents of France (non EU)...
you must obtain a French license 1 year after moving here on a permanent basis. I goofed up on that one, as I wasn't aware of it for about 3 years ...so continued to drive on my American license with no problem. When I went to the Prefecture to apply for a French one, they weren't going to give me one because it was beyond 1 year, however, being the pushy American I am, I just refused to take no for an answer and bugged them several times...they kept saying no..but about 2 months later, I received the notice to appear for my medical (very simple eye test and blood pressure) and was immediately issued my French driving license. As a French woman told me a few years ago, never take no for an answer in France! I think this will continue to apply for UK expats. Take a deep breath and don't let the scaremongers get to you!