In years gone by, American friends of mine got considerably better service from BA than friends living in the country. The BA Miles scheme also rewarded them better. So much so that, one friend here, relocated himself to friends in the US, as far as Exec Club were concerned. He got metter milage rewards for a number of years, before they started to cut it all back.
Without raking over all the details NotDanish, it is very curious that your bank process the charge without checking that it was correct. In the UK, my bank would not permit me to go overdrawn in such a manner - they would have bounced the charge. Now that, of itself, would have produced a penalty payment that I would have had to reclaim from the merchant involved but it would not be as problematical as having a 700/7000 error trash my bank account.
Sounds like BA have done the decent thing.