Disagree, the passenger flow with the bolt ons to the 1977 structure are convoluted and the place is just too busy. There's only so many add ons you can do before it breaks down. See LHR pre T5 and now MAN then compare with LHR T5/T2 and BHX post rebuild. Even GLA used to put L1011s in Gate 1 with three wide bodies at the end of the old intl pier. Possible? Yes. Good customer experience? Hell no.
Time to rebuild.
Compared to some German or Swiss airports, the UK just hasn't a clue.