Originally Posted by
stut
It's past immigration - all arrivals facilities are apart from the exit-through-the-gift-shop. IIRC on a mezzanine level, but well enough signed.
The AA arrivals lounge is at the mezzanine level. Upon exiting customs in T3, you pass the last duty free pitch and come through one of the two sets of double doors; Marks & Spencer is on the left. If exiting via the people gate immediately to the after going through the doors, walk straight ahead towards WH Smith, once past the seating area, go to the right and take the elevator (on the right) up to the mezz. level.