Originally Posted by JDiver

This is a frequently asked question. Most consider it more expeditious to go to T-5 and shower in the Galleries lounges there after following the Flight Connections signs to bus to T-5.

The alternative is processing HM immigration (can waste an hour here) and customs, followed by the Arrivals Lounge, trek to the train, arrive T-5 and process as if you were starting your trip de novo. IMO, even Fast Track can be slow - or Fast Track can be closed on occasion.

The showers are better in the Admirals Club and Arrivals Lounge, but in my experience not worth the extra hassle of doubling back as described in the "LHR / London Heathrow AA T3 <--> BA T5 connection / transfer master thread" thread.

Specific descriptions can be read in the LHR Club and LHR Arrivals lounges threads accessible from the Lounge Dashboard in the Welcome "sticky" thread.