I am also from Greece. Yes there are laws in place, but unfortunately they are not enforced.
Stay away from flying over crowds/cities/airports and you should be fine. The law does not allow to fly over:
military bases, hospitals, archaeological sites, prisons, airports and some other points.
In general, try flying under 120m which is the maximum allowed altitude (if I can recall correctly) but try to fly high enough so that no one will be disturbed (let's say more than 50-60 meters). Fly responsibly and nobody will bother. I think you are obliged to keep VLOS.
I try to avoid taking off in front of people, I just don't like to have people or children around me asking things when I try to focus on my flight. We have some very good places for you to capture. Happy Vacations!