Battery Recycling in Greece
According to this article (in Greek) about Battery Recycling in Greece (ΑΝΑΚΥΚΛΩΣΗ ΜΠΑΤΑΡΙΩΝ), there are two chainstores (Carrefour and Praktiker) who accept used batteries and will properly ship them off for recycling. The article also gives a lot of background information about the problems with toxic battery waste. And it mentions several ways for people to get into action about it. First thing for me: I'll find a Carrefour so I can properly dispose the old batteries I have lying around. I'll also read more on the site itself, since they have lots of information about Recycling in Greece in general.
Just seen that Carrefour really mentions battery recycling on their website. So it looks like that piece of information is correct. Still, don't forget to use as few batteries as possible.