The problem is that there is nowhere to wait for the toilet except within the galley, as the aisle is too narrow. I was last on BA's A350 in 2019 when it was nearly new, and on that flight whilst waiting for the forward toilet the crew jokingly asked me if I'd like to help them with the service, since I was in the galley! (they were juggling 50 or so desserts at the time, with plates stacked on every available surface). The lack of preparation space was obvious from the start, on that particular flight I was chatting to the captain who was very enthusiastic about his new aircraft, but said he wished BA had allowed more space for the cabin crew to work in, you'd hope that BA would listen to this sort of feedback from their employees.