If you can stomach being a frequent flyer on American, then you get credentials to enter the BA lounges at Heathrow. Not exactly the rock-n-roll life of the Virgin lounge, but quite luxe. Read more
Very nasty crowded and dirtylounge I do not see the point of paying extra on a ticket when the lounge service is rubbish and asking you to go early to your gate so they can have empty chairs!
Double check your flight isn't leaving from b gates ad this is an extra train ride and can leave you pretty short of time - there is another lounge at b gates