Originally Posted by
Himeno
Might not help but...
I normally have a morning BA arrival into T5 and an afternoon or evening flight out of T3. I tend to go through immigration and use the BA arrivals lounge in T5 (shower, breakfast), then get the train over to T3 and use the lounges there.
There is the AA arrivals lounge in T3...
^^
Plus the AA lounge will give you the neat drink tickets since you're on Intl travel, which means you get a champagne breakfast.