In my Compendium of On-Line Soil Survey information at
http://www.itc.nl/~rossiter/research/rsrch_ss.html
you can find some sources on soils in France at:
http://www.itc.nl/~rossiter/research/rsrch_ss_sources.html#eu_f
There is a soil map of France which is mentioned there, specifically by the Unit de Science du sol -
Service d'tude des sols et de la carte pdologique de France (SESCPF) at
http://compact.jouy.inra.fr:8888/compact/consulter/externe/unites/ecrans/272
I assume you can read French. Bonne chance!