I can second it. The website is full of useful information (particulary if you never been to Greece) and Diederik (I believe is his name) is very helpful. He recommended us a few smaller charter companies and we eventually went with one of them. Pretty happy about it. And Diederik was very helpful with variety of questions I had about sailing in Greece (it was our first time there and I hope not the last one . If you never been in Greece, I highly recommend chartering boat there because you can combine your sailing trip with sightseeing of a lot of historic places. It is in fact a birthplace of Western civilization.A site which can give you some reviews of charter companies is:
Yacht charter Greece and sailing holidays Greece and Turkey - Marine navigation - Yacht charters Greek islands and Turkish coasts
We used him 6 years ago before we did a flotilla charter in the western areas.
Best of luck.
And you are not by any chance related with those companies?If you are not satisfied by either of the two:
Yacht charter Greece , bareboats and crewed yachts
Nomicos Yachts Ltd.
you will not be satisfied by anyone else.
Sailing out of Alimos marina near Athens provides for best combination of boat variety and charter price.