Originally Posted by Neil Lawton

Problem resolved, hopefully. After an hour on the phone to the local BA Bangkok/Indian Call center office (toll free), I managed to book the wife's seat, it was important that we sit together for medical reasons. The guy at BA said that there is a known problem with the manage my booking tool, once some flights have been amended, this should get sorted within 48 hours, we will wait and see! Surprisingly, despite booking through a travel agent, in the end BA did want to help, it just took a lot of emails and phone calls to get this sorted!