The greek has a different fare structure to nigels and really they don't have to rebook you AT ALL. It's not their problem, and even without refunds BA has lost a massive whack as a result of this crapology. Also BA 'owns' PART of a PART of NATS (No Air Travel Service).
I wonder what MOL's positions was on refunds etc. I heard stories of flights disappearing off screens and people not knowing what had happened.I have had an experience where my flight was cancelled as a direct result of THEIR shoddy tech work, and we offered seats on the next flight. A flight which was longer selling!!!!!
If you went with Ba at least you'd get there or rebooked for another day.