Been researching a sail trip to Greece for next year. There are a bunch or charter companies that you can go with. Moorings and sunsail will leave out of Corfu (access to northern Ionian islands) and Athens (access to Saronic, Argolic gulfs and Cyclades). You should also check out Dream Yacht charters. I have used them twice in Genada and have booked a charter in BVI and they are good/as good as moorings. They also have a lot more bases including Corfu, Lefkas and Prevesa in Ionian. They also have a base in Lavrion Greece near Athens which is 40 mins from the Athens airport and easy access to Cyclades. They also have bases in Cylades and the Dodecanese islands, northern sporades as well.

A couple of sites that could help your research

cruiser's forum Mediterranean forum search key word greece, ionion, cyclades, etc - https://www.cruisersforum.com/forums/f17/

Sailing issues has a lot of information on sailingand chartering in greece and details on the regions and islands - https://www.sailingissues.com/greek.html


good luck!