So I rocked up at LHR as advised by the call centre staff and surprise surprise the ticketing desk couldn’t change the flight to an earlier one either. I was told that since it’s a promotional A fare, free changes on the same day are not allowed and I was offered the change for £190 which I declined and called Aegean again. 20 minutes on the phone and they concluded there is a system problem and offered me the 16:35 flight which I declined as I have an evening connection out of Athens. I insisted on the 12:15 departure as I was already at LHR with 3 hours spare. They promised a callback and indeed 10 minutes later they rang back and my 22:15 ticket has been cancelled and replaced with 12:15 so I was able to check in and now I’m on the plane enjoying the covid pre-departure drink aka nothing.