In general, I have to say that this thread serves as a reminder that one should really watch their timing in T5 on BA. I usually fly Star Alliance out of T2 but recently had an early morning BA flight - it was from the C gates and was quite surprised how long some of the travel times from lounge to gate are especially when one has to take the train. In my case I was at the B-Gate lounges and then just missed the train, so waiting a while for the next one I could board. So one should definitely err on the side of caution in T5.