HI
I need to go to LAX from UK in summer 2023 and the prices out of Madrid and/or Dublin with BA/AA are almost half the price going from MAN in J. Might make a JFK stop to maximise tier points to get BA Gold again. (Ex EU-LHR-JFK-LAX and return- the wife will hate me for this

)
But I want to pay in GBP rather than EUR on my AMEX BA card towards getting another 2-4-1 voucher.
Any way of doing this online or is it ring BA and see what they offer?
Never done this before, so not sure.
Any advice will be greatly received.
Thank you