Thanks Reka, i've tried all those obvious places, but I cant find a cake board anywhere!

I would recommend you Allegro..... (maybe Alligro) can't remember the correct spelling.... but most cooking supplies for baking, grilling, boiling etc. etc. can be found in Allegro.

I am almost sure you'll find them there because they catter mostly to restaurants, chefs, and big food producing companies...... but you can also buy for personal use as well.

Loups, have you tried IKEA and sometimes Casa?

Not been there for a while but would suggest trying  Girard aux Grottes, Rue des Grottes 6, 1201 Genève 022 733 62 20

If they don't have what you are looking for, maybe they may be able to tell you where to find it..?

 Aligro have some suitable for pies, not at all suitable for multi tiered and heavily decorated cakes. My advice, order on line have them delivered to France, thats what I always do unless I make a trip to London.