France has a lot of military airspace (east and west, less so down the middle) but a lot of it is inactive at weekends.
You need the SIA 1:1M VFR charts (available for about 30 euros from the SIA online shop - 1st item on
this list) and these come with a booklet which states, for each R( ) area when it is active. Also, the regional FIS services will tell you if/when some area is active, and there are even phone numbers for some of these. The Cazaux stuff is not very useful because by the time you are within VHF range it is too late to re-route substantially.
If one can fly at a higher level, there are the Class E routes, FL065-FL105, which avoid most of the mil airspace. UK PPLs often call them "airways" but Class E is uncontrolled airspace for VFR. These routes tend to run between the VORs so you get the bonus of an easy VOR backup for GPS. The rather pretty IGN charts, popular with VFR pilots, don't show these routes though...