I am a yacht aster instructor and examiner (retired), and spend a several months a year sailing my own boat in Greece
I would consider doing a Day Skipper
course, shore based over the winter, and then do the practical at a uk ,tidal, RYA sailing school
Having done that boat handling and mooring
in Greece also needs practice and experience.
One of the most basic and essential requirements is wind
awareness and in particular reversing whilst laying an anchor
and going "stern to".
in Greece is a way of life and must become second nature. Most town quays that you will visit in the Ionoian or Agean will be crowded, and mooring
can be stressfull until you become used to it.
Having said all that Greece is an amazing sailing area, and so enjoy.
My boat presently in the Agean is names Josephine. If you see us come and say hello.