That makes sense and is timed with the late LHR departures. I left around 22:30 last week and was able to order food at 22:00 without issue / buffet was open, though the server said the orders were shutting down. The former AC space was being packed up when I left.

What was odd was that the concourse C AC had no times listed as those hours of operations signs by the door / elevator were covered with paper.