My last ticket ('04), BA CAI managed to charge me in GBP on my Amex - an arrangement I was very happy with. I'm still using my Amex this time as the £3K is valuable in getting to my £15K for the 2-4-1, not to mention the Airmiles. Though, this will load the ticket cost by about 3%

That's about £100 for 10K miles (1p/mile) and a leg up to the 2-4-1