Hi grimpeur,
I am a boulderer from Greece and some German friends and myself developed most of the problems there. There are about 600 probs and scope for thousands. There is a very good guidebook from these German friends I already mentioned (Karsten Oelze and Harald Roker).
www.gebro-verlag.de The best season to go there is winter since Greece is very hot in the summer even very early in the morning.
There are also some very nice bouldering areas in North Greece( Check out the same site for Olympic blocks). Don't hesitate to contact me if you want any further info...