If you don't have the waze app on your phone it might be worth installing. There are a lot of Waze users in France, and it's a very useful aid for getting a heads up about accidents, hold-ups and speed traps/police up ahead. I also find the fact that it gives you an audible warning when you've gone over the speed limit a useful reminder. I find it's reactivity to traffic hold-ups far more up to the minute than the expensive "intelligent" Garmin GPS systems in our Mercs.
You'll find that on waze in France fixed cameras are often pinged as police, as the site cannot show the exact location of speed cameras, so other was users ping them as police to give the exact location.
