Originally Posted by
wrp96
It wouldn't have helped anyways. The Priority Pass lounges are airside and you won't have access to those lounges without a departure from those terminals.
Broadly speaking, once you are airside at T5 you are now allowed to go to the pay as you go lounges in the other terminals, and then to return. There are even HAL signs up to facilitate this. The one exception is T5 Aspire, you have to be departing T5 to use that one.