Try here first
http://www.aviation-civile.gouv.fr/
I haven't any experience of sitting the exams in France but here in the uk exam slots are very hard to get and there are several months waiting lists.
You really need to plan which modules to sit and get dates booked for them before your visit.
It is possible to sit and pass all the B1 exams in 6 months so long as you spend a long time doing in depth study beforehand.
Good luck and let us know how you get on
