hmm. having had familiy grow up and fly off, I haven't been to rural France for a bit - when I looked up 2 of the places I remembered fondly, they've gone rather upmarket.
nevertheless they are well away from large towns and still relatively small by French standards, here they are for what they're worth:-
http://www.lestilleuls-roca.com/
near the medieval town of rocamadour, the gouffre padirac showcave and within the causses du quercy regional park
http://www.camping-roc-qui-parle-aveyron.com/
at Nant in the Grandes Causses, not far from Millau and the Gorges du Tarn, Dargilan, Chaos de Montpellier and Roquefort.