I will only add to the comments above that at T4 there is a tiny area at the front of what is actually quite a small airport terminal, so it really doesn't matter where you stand, you'll see the bus roll through and will be able to walk to the bus before it opens the door.

From T5 it is a little more complicated since (a) it's bigger and (b) H30 goes from a separate but close by stop/stand/stance This is the current set-up but like supermarkets then tend to shuffle things around from time to time.