Originally Posted by orbitmic

I think you are correct on the second point, though it still doesn't make sense for the avios difference. The OP is confusing because the question contradicts the description in the situation in the next sentence (bolding mine) so I think that the OP needs to clarify.



In short:

- Upgrading a RFS means you booked a RFS award ticket and then decide to upgrade its class of travel: in effect, this will normally be effected as a cancel and rebook by the way. In that case, you'll indeed pay the difference in RFS award level and taxes at whatever rates you choose plus the relevant cancel/change fees.

- Upgrading a cash ticket to a higher class: this is quite different obviously but should still be based on the standard avios rate, not the avios+£1 rate so it seems to me that the OP has been overcharged.