It was alongside all the others on the far right @
madfish .... came up escalator (from rugby scrum of two buses which were parked facing each other when I got off the plane !), then turned left and they were all in front. From memory (and it was a 5 large Johnie Black and 01:00 memory), there was a connecting door going off to the right behind the Transit booth.
No question this particular Passport Control was at the very end (plane end not baggage end) of the terminal building. Perhaps above Gate 32 which BA885 left from this morning.