Originally Posted by
Airprox
BA will be using the official IATA exchange rate which is updated daily, not some random internal exchange rate they have made up for their benefit.
Indeed, and it is likely to be better than the start point than whatever the credit card company uses, to then add the 3% uplift. So it is worth calculating the booking fee through to see if it is worth doing. This isn't guaranteed, but it seems that ticketing agents at LHR don't always collect the £15 fee there, so long as you butter them up a bit.