Originally Posted by
citiflyerUK
Looking at the same flights J is just £680ish on the way out. Is the upgrade cost , if I call BA likely to be the difference between what we paid and that fare? (I.e. no more than that?)
No, it is more complex than simply taking the fare difference. You will also need to pay a change fee. Calling BA is your best bet.
At the airport they may offer discount upgrades, but this is not guaranteed, and it may be no cheaper than what can be offered over the phone in advance.
If you have sufficient avios, you could look to upgrade to WT+ and then hope for CW award availability to upgrade to with avios.