Agree with Langcliffe. Chartreuse is an excellent venue and has loads of high quality, undervisited (by Brits at least) caves. Vercors is good but overly popular e.g. Gouffre Berger - there is more to France than Vercors.
The Dent de Crolle system is a well known, well visited classic in Chartreuse and I can recommend the P40 - Trou de Glaz - Guiers Mort combo (took about 4 hours excluding the walk up to the P40) and the Grotte Chevalier (huge).
However, there are many other excellent caves described in Langcliffe's references.