Hi Paul, It all depends on which route you will be taking and how many hours/ miles you want to cover before stopping. And cou,ld posibly norrow it down a bit.
If your going acros France then there are a lot of good sites around Troyes9 , If your going North and through Belgium, less toll roads, then Colmar and Strasbourge are good areas, lots of municiple sites both ways.
Hutch.