I just called BA and I asked them if I book a flight from LON to MIL and pay cash and use my miles to upgrade to business, if I could change my flight later on in case I need to and how much I would need to pay.
The girl replied saying I can only change 24h BEFORE the flight and not after and it would be £31.
Is this right? You can't change a BA european flight?! This seems ridiculous!