Your headline is confusing and misleading. T5’ s transfer process I feel is clear, organised, straightforward.. and as a UK National, seamless going from Domestic-to-International when you compare, say, Toronto Pearson. And international-to-Domestic is a necessary Security check in top of Border Control.

bear in mind, the security check on international inbound arrivals-to-connecting flights are considered necessary due to perceived lesser standards from the departing country. That side, I’d rather every passenger had comfort in safety than gung-ho doesn’t matter.

as far as weather, rain, delays, etc. hardly T5’s fault.. that’s ATC, airline, inbound delay, crew factors and nothing to do with the transfer process in-terminal.

i personally prefer the T5 transfer format, layout, etc than that of a lot of airports in the world. It just needs more space now, and less shops