As I live very close by to LHR, I don't usually bother with arrivals lounges but there used to be a lounge in the Queens Building, between T1 and T2 but the maps on the BAA website do not cover that building! I used to access it with my Priority Pass for departures. Likewise, I don't need to snooze there so can't help on that one.
There is a Servisair paid-for lounge in T1 that is bookable through this link. I know the link says 'parking' that's just because the BAA pages give you links to book lounges (which work) but they say
parking more than they say
lounge. Just consider it a way to park your ...
B A A airports official parking: B A A Advance