Driving in France is no problem as unless you have a LHD vehicle you as the driver will be sitting next to the kerb. If you are positioned ok for the kerb the traffic coming towards you will have plenty of room.
Caz is correct when he says beware first thing in a morning but I find that only applies if I'm coming out from the campsite onto an empty road. Similarly if you've been for fuel and pull off the forecourt into an empty road. If there is traffic on the road you are ok. But yes keep your concentration and don't give yourself overlong journeys without rest stops.
Best time to go? To a large extent this depends on family circumstances but May/June is a good time to go. Campsites have plenty of room so you don't need to book and Camping Cheques is a good way finding excellent sites across the whole of France at a reduced price.
Be flexible.
We go for a month 3 times a year and have no fixed ideas about where we are going. Most of France is very motorhome friendly, if you don't want a campsite there are plenty of places to dump grey and black water and to fill up with clean.
Best area to go?
France is a large Country and there are big differences between the various regions. The differences are in terrain, in food, in wine, in history, in wildlife, in climate, in...........I can go on for ages. We have been going to France since 1978 and never tire of it. The one thing you must give yourself is time. Treat the whole of your time in France as part of the journey of discovery.
You've got me going again! Roll on March and our first trip this year.
Keep asking the questions. There are plenty of folk about with answers.
Gillian