Just another point if you arrive at a busy time. Heathrow has been having some long queues at passport control and the split between 'connections' and the 'border' at T5A is not as obvious as it could be. Mainly this is because the queue starts before any of the signs separate. As an international-international flight connection you do not have to queue for the border but lots of people were getting that wrong the other day and having to be pulled out the queue by BA staff so don't queue unneccesarily . Good Luck