In May last year I crewed in a 34ft 1950s wooden yacht from Dubrovnik to Corfu. We weren't hailed by the Greek Navy as we passed Ag. Stephanos although we heard other larger craft being asked for details.
Near Nissaki our engine seized and we were becalmed. The engine had been "reconditioned" in Croatia and had run only 60 or so hours (Keith the UK mechanic at Gouvia was amazed it had run that much when he stripped the engine). We had our Q flag flying and contacted Gouvia for advice. They suggested we get a tow straight to the marina. When we mentioned customs etc they said we could go directly to Gouvia and report to Customs the following day.
The next day at Gouvia we checked in with the Navy bloke there in the little office in the marina. He was extremely friendly and very laid back indeed. We mentioned VAT and he told us to go to the main Port just outside Corfu Town. On arrival there we spent about 30 minutes wandering around trying to find out who to report to. We eventually found an official who asked us the nationality of the skipper (English) and the flag of the boat (UK). He then told us to go away.
I know that regulations exist but I think you'll find they are not usually applied
in Corfu :)