I have been wondering the same and emailed them on Monday but haven't had a reply either. I've booked the rest of our holiday and just want to book our first week at Moulin de Paulhiac now so that I can really begin to get exited about my summer hols.
AFAIK the couple that run the site work in the Grenoble region during the skiing season each winter - leastways they did when we used to go there 1999 - 2002. I think it was mid Feb before we got booking confirmations - and we used to go late May / early June.
Don't forget to leave a review of the French and other European campsites you have visited!
Amazing family weekend with old steam engines, classic car displays, market stalls, and full catering and bar. And camping on site - Save £25 by booking in advance.