I'm happy to report that Olympic came through!

They contacted me about the booking and offered me the choice of a refund or rebooking. I asked to be rebooked on an AF (outgoing) and KL (incoming) flights. They accepted and I just received a new ticket. AF in E class, KL in Q class.

So while I'm quite happy about that, prices have increased tremendously and for the rest of my travel to ATH I'm pretty much screwed. Unless somebody indeed adds flights..