Judging by the size of the specimen and the shape of the teeth, I think it's a mandible from a groundhog. and mostly complete, just missing structures on the back. Check out the photos here to see a full mandible.http://www.thefossilforum.com/index.php?/topic/22051-help-to-identify-jaw-bone/
I don't think there are any wild populations of goats on the islands of greece, only domestic goats and feral populations. The mountain goat usually refers to the white North American animal Oreamnos americanus and not member of the same genus as goats.
Looking at the overall shape and number of teeth I'd say you have a raccoon skull. Canids have four premolars and 3 molars, raccoons have 2 molars like this guy. Also the red fox has a more elongated skull. Hope that helps clarify. And great job cleaning, looks perfect.
It is definitely a vole, the only question is which. The good thing is you can ID from molars. From consulting my field guide I'm gonna go with meadow vole. I could only find upper tooth row drawings and photos but the meadow vole's looks the most similar.