Don't think you're crazy to try. After all most of the French don't stay in hotels during their vacations; they stay at family owned homes, campgrounds, gites & so forth. A good B&B guide would be a help & of course you'll have your Logis de France book. ← Sounds familiar, except chez nous my wife gets antsy about 3 PM and insists I start telephoning Gites/B&B's/posadas/agriturismo's/etc. In decades we've never slept in the car, have rarely not found a great place and except for trips when she thinks we need a "base" from which to operate, don't get reservations ahead. Now, we carry a library with us: in addition to food guides, the Michelin, Gites of France, Karen Brown, Logis de France, etc. The problem is not one of reality but comfort level with uncertainty. ← It all depends on when in August you are planning on doing the drive down to Spain. Sunday is a great day for travelling as there are a lot less trucks on the road. If you are planning to following the suggestion of going to Millau and then down to Barcelona can I suggest you look at our place as a potential night stop? (I hope this is okay for me to do as I am new to this forum, and don't know if I can mention our own establishment as a recommendation? I did not come to the forum to promote ourselves, but to actually discover hidden gems in the area we live.) We are in Pezenas which is 1.5 hours from the Millau bridge and then 3.5 hours to Barcelona. You can check us out on our web site. our place is called Hotel de Vigniamont. Another great guide book is Alistair Sawday Special Places to stay. There is a b&b guide and also a chateau/inns/special places. They have a web site with quite a lot of the properties listed.