Having the AMX-P or AMX Gold card gives you the priority pass.
Pls see link below, embedded is a priority pass link which will list
the lounges available

http://www.americanexpress.com/lacidc/en/laccards/viplounges.shtml



Lounge available at Heathrow: Terminal 1 with Priority pass:

http://www.prioritypass.com/lounges/lounge-details.cfm

Lounge available at Terminal 3:

http://www.prioritypass.com/lounges/lounge-details.cfm

http://www.prioritypass.com/lounges/lounge-details.cfm

http://www.prioritypass.com/lounges/lounge-details.cfm