I am also looking to adjust my destination. My ticket is open-jaw (booked for 2 pax using a USA Chase BA companion cert, FWTW). I'd like to make the return jaw shorter, ie. return from Italy, not Greece. Our origin is in the USA, and we connect in LHR in both directions.

It would seem better to throw away the Greece-LHR leg and just get myself to LHR, than fly from France/Italy to Greece just to connect back on a 4h CW flight.

Anyone have experience with BA waiving their "zone changed must cancel and rebook" policy? what if I try this at the airport? Or if I ask to have the ATH-LHR leg deleted entirely? Or if I simply don't show up for it?

Thanks.