Hi
Greetings from France itself.
Everything you've heard so far is spot on. This is a lovely country for cycling. It does vary hugely from one area to another, though, so which way you ride will affect the nature of your ride.
If you ride down the western edge of France, for instance, your ride will be a lot flatter than riding through the Massif Central and it foothills towards the centre. You will have lots of pine forests (especially in the Landes, the largest forest in Europe) but, after a few days, not al lot of stimulation.
The Massif is harder and more remote and you'll make far slower and more tiring progress. But you'll feel you've seen and experienced something far different from home.
Eastern France is harder to travel, especially close to the Alps, because the Rhône valley is tightly packed, heavily built up and heaving with traffic. The valleys also tend to run at 90 degrees to your intended direction, so you'll be riding across the grain. Do go that way if you wish but certainly avoid July and August.
The Pyrénées are lovely wherever you cross and the choice is yours. The northern side of France, though, is quite the opposite: flattish, open, rolling, often windy and, to be honest, often rather dull. Little is more disspiriting than a day of headwinds across the plains of Picardie or a rainstorm in the Nord area between Calais and Lens (where the tourist people are so stuck for highlights to advertise that the motorway-side signs point out **** heaps from the old coal mines!
(But do visit the graveyard at Sallaumines, Lens, and pay homage to Maurice Garin, first winner of the Tour de France.)
You'll find camp sites almost everywhere in France. Many are shown on Michelin maps (or, at least, villages with sites are indicated by a little tent icon). But these are just a fraction of what's available and around one in three villages will be able to help. Happily, the French for a camp site is 'un camping'!
Final hint (ask if I can help you more): if you need water, stop at any cemetery. They all have fresh-water taps.
happy days
les