In the end I got my money back from Public but not before they gave a three hour run around. When I went there ate 11am the shop assistant told me rather snottily that I couldn't exchange the camera until the technician arrived at 1.30pm so rather than drive across town twice I hung around the mall. When I returned the technician told me to go to the sales assistant who'd sold me the camera (so why did I have to wait two and a half hours?) who told me to go to the technician and so on and for forth for about 20 minutes.
After all this the last thing I wanted to do is wait a week (maybe more) for them to find another camera of the same make. It then took them another 20 minutes to figure out how to cancel my sale which had been done via credit card. All in all, a frustrating and time consuming experience.
So take my advice and avoid Public, Thessaloniki at all costs.