Probably too late to be helpful but for future reference The problem with southern France is the terrible busses, they rarely cross departmental borders and often only serve the local market town once a week. That said the Herault does seem to have some better buss routes as Ani said. I’ll actually be setting myself up with a base in Beziers next year, but that’s a bit bigger than a village
The real hidden gem is that there’s still some underutilised regional rural railways, indeed whilst Beziers is a bit far from the hills for biking, in Languedoc-Rousillion (maybe Midi-Pyreenes soon too now they’ve merged) the train tickets are only 1€ (from the red machines), and in fact also 1€ on the main lines (but you have to print your own ticket and there’s limited numbers). I plan to simply hop on the train up to the gorges and plateaus near Bedarieux to do my biking from there.
I’ve lived around the Cevennes and Salagou and find that it tends to get a bit too hot and dry in the summer, but if you know where to go there are some nice cold streams and pools (usually with too many tourists in Aug). Nonetheless checkout all the villages along these lines as they get several trains/busses a day and you can surely find somewhere great. I’d also suggest investigating Le Puy-en-Velay, which is 2h train from Lyon and great for the greener summer countryside. Whilst it is a town, there are neighbouring villages but most of these towns wherever, are so small and lacking in suburbs that you can escape in a few minutes on foot. France is blessed with multitudinous well-marked walking paths.
Currently I’m in Carcassonne (same as Beziers it’s 2h direct train to BCN should you need big city life, but here also has all-year Ryanair connections) and whilst the countryside isn’t spectacular it entertains me more than enough. You can even swim in the river right here in town, as if you were in the countryside. Here’s a map with the cheap lines, but also look at the quiet lines north of Toulouse (it has a major airport). I wouldn’t rule out all the towns! Also have a look around the Vercors/Aspres-sur-Buech/Sisteron (in the Rhone-Alpes/Provence). I’ve also visited Jon and the guys in Javea and it was great but maybe not as secluded as you’re looking for? There’s places to retreat even near Berlin: http://coconat-space.com