Originally Posted by
Jagboi
When you bought the ticket did you buy it on the UK or USA site of BA? Was the charge originally in GBP or USD?
Irrespective of the BA country website OP would have purchased it from, if his booking was indeed an ex-UK/Channel Islands/IOM/Gibraltar itinerary, it would have charged him in GBP regardless of whether that was booked through BA’s UK/US/Irish/Indian/Spanish/etc websites.
Only scenarios where it might’ve not have been charged in GBP would’ve been if the booking was made via non-UK BA phone lines/ticket offices or non-BA channels like travel agencies or an Avios booking.