Sycamore,
My recollection is hazy but I believe that there are considerable restrictions in France about off-airfield landings. One of the French Government Departments issues (after considerable delay) a helisurface permit (or something like that). This authorises you to make off-airfield landings but I think you are supposed to contact the local mayor for each landing.
As you can see, my memory is not perfect, but some years ago I planned a trip similar to yours and was pointed down this route.
I hope someone else can firm up on these issues for you. Perhaps a French pilot/operator could assist?