I have reported this problem for US residents here last October and asked for help with work-arounds, but nothing that was suggested (using a VPN, changing my location to UK, etc.) etc. worked. As soon as I logged in to my BAEC account, as one must when dealing with Avios purchase or spend, the price changed from ££ to $$$$. It seems they were using an old (2021) exchange rate of 1.38 or 1.4, at a time last autumn when the Pound was down to $1.10 US.

Some on my thread compared it to Apple price-gouging UK customers, and I sympathize, but might this be a matter of tariffs and taxes rather than an improper calculation of the exchange rate?