Ambassador, British Airways; FlyerTalk Posting Legend
Join Date: Apr 2012
Location: Leeds, UK
Programs: BA GGL/CCR, GfL, HH Diamond
Posts: 42,964
1. Not possible, to go airside at T5 you need to have a bp for a flight leaving T5. You need to check in and go airside at T3.
3. Actually you have no choice on this one if you want to use an arrivals lounge since the AA one in T3 is closed for refurbishment so all eligible passengers must go over to T5 to use BA's arrival lounge.