Hi all,

Is there any way to check the taxes and fees payable if I were to upgrade one leg of a return flight (BA, paid in cash) from WTP to business?
I know the amount of Avios required (difference for that leg between WTP and business, around 25k in my case) but know idea about additional taxes/fees.

Tried calling BAEC but no one picking up / able to check.

I don't want to buy it only to realize the fees are too high.

For reference, I am buying a ticket (in cash) from LON to NYC, return (on BA)
Outbound would be economy, return premium economy (WTP).

I'd only be upgrading the return flight.

Any way to check the additional fees/taxes due?
Does anyone have an estimate (for 2022)?

Also, how would I even book the upgrade if no one is picking up (I hear it is not always possible on the website)?

Thank you!