The French police are getting very strict on a lot of things, and they issue on-the-spot fines that are just as they say: on-the-spot. Don't have the cash on you? They'll give you a lift to a cash machine - how you get back to your vehicle is up to you.
If you exceed the speed limit to excess, they can (and will) confiscate your vehicle. For good. Full stop.
And on the subject of speed, if your GPS receiver has speed camera locations recorded in it, that's also now illegal.
I'll be driving through France to get to Switzerland later in the year - must get hold of a breath kit. And a high viz for each person in the car. And all the other stuff we need to carry.