I have found the links for the Flying Cat and the Flying Dolphin from Pireus so answered by own question about how to get there, however in September approximately 12/9/2011 would the ferries still be running a number of times a day as they are in April.
Also would all the restaurants etc still be open or would the island be winding down. We were thinking about spendidng perhaps 7 days there but would not enjoy it if there arent a number of restaurants to choose from or if the island is too quiet with not many people at dinner in the restaurants etc. We hate to be the only ones in a restaurant as we enjoy the atmosphere of a busy restaurant for dinner.
Thank you for all your advice. Hydra sounds lovely but not sure whether to try to fit in as one of 5/6 islands to visit in September.