When are you travelling? In winter, low season, or high season? This makes all the difference to recommendations for sites, I think. Lots of French sites, particularly the smaller ones, have very short opening dates. Give us an idea of your plans.
Or, have a look at the www.campingcheque.co.uk, or www.campingcard.com websites. Both have maps where you can find sites, and have a look at the facilities and the opening dates. Both schemes will cost you no more than 15 euros per night for a pitch, car and caravan, awning, electricity, and two people (plus a dog if you have one). Some ACSI sites are as little as 11 euros.