The apt is in a great location. DO NOT arrive late, subway does not run after 11:30, and most buses do not run after midnight. So Manos directions will not work for you. If you must arrive late, just take a taxi from Syntagma Square to the apartment. Verify with Manos that someone has checked the lock box to ensure the keys are in the lock box.
The apt was clean and in a great location for getting around the sites in Athens.
Never met Manos but his Dad and the young lady in the shop that helped me, were very nice.