does anyone have a contact number or address for the french jewellery
designer Servane Gaxotte who is based in Paris?

Don't know if this is the contact you are looking for but there is a
Gaxotte Productions listed in the Paris yellow pages under COSTUME
JEWELLERY (MANUFACTURE AND WHOLESALE). Their contact info is:

Gaxotte Productions
154 rue Oberkampf
75011 PARIS
ph: 01 43 14 91 02

Good luck.

Cheers,
Trevor F.