There are still a great many places where we haven't been camping in France yet and at our age I doubt that we will stay in them all by any means....all say Ahhhhh! But by the same token there are a great many places where we have been and most of them have proved to be very enjoyable. Everyone has their favourite places I suppose and ours is the Vendee, closely followed by Charente, but this page is about France in general rather than specific areas.
Camping holidays down the Western coast of France are (usually) achievable in one day from your point of departure in the UK depending on which ferry you catch to land you at St Malo, for preference. I believe that Brittany Feries drop off there about 9 am ish which gives you easily enough time to get beyond Bordeaux and as far as the Northern Spanish border. Condor Ferries drop you off at about 7.30 pm French time at St Malo which is just about enough time to allow you to get to the La Tranche or St Jean de Monts areas of the Vendee before 11 pm when the camping site barriers come down for the night.
For camping in the South of France you may well be best served by taking the Dover/Calais crossing and bombing down the Autoroutes, though I doubt that you can make it in one day, and you really must take care with your speed on them because the cops have recently started timing vehicles from when they pay to the point where they turn off: take an average speed from that time and you are booked mate - big heavy on the spot fine payable in Euros. You have been warned! More of that sort of thing in our page which gives good holiday tips.
We have been camping in Spain and Italy and in another life I was camping (as part of the job in those days) pretty much all over the globe which included some rather nasty places, but we always, always come back to France for holidays these days, and that is not just because France is virtually on the doorstep it's because of a great many factors, one of which is that the standard of camping sites and the companies which use those sites is the highest we have come across.
Please have a good look at our page about European driving laws which we have put together specially for your benefit. There is also a link through to the AA site from there where you can get all the official info you want for any country in Europe. Another page we have dredged our collective minds to produce is probably the most useful and informative page for the newbie camper is our page about camping etiquette.