British airline can cancel your seat even if you paid for extra leg seat without any explanation. They are not responsible people and please try to avoid booking with them. I have not experienced with other airline and this is my first time and my last. They just ask you to submit your claim. I booked 3 months in advance and was not told of seat changes. Did not explain why they are doing it and just ket you have an ordinary seat. Even when I arrived in London they don’t want to compensate you on the spot and if you don’t claim with them they just don’t care. They give you the phone number to call. Would you call if you are back home? Lousy service on the BA Staff. Never will fly with BA again