In reply to fxceltic: Ha! Thinking about making the very same trip, (Biarritz and the Pyrenees are great), which I last did 18 years ago with my eldest son in a very slow campervan - so several stops.
From memory we stayed on the cost near Bordeaux where there are huge sand dunes, further north we stayed in a beautiful campsite in the grounds of a chateaux in Limousin, b*ggered if I can remember the name of it though so not much help I'm afraid. I'll probably invest in a book of French campsites, if I recognise where we stayed I'll let you know.