It appears the LHR T2 Priority Pass arrivals lounge is now open:

http://www.plaza-network.com/locatio...il?city=London

And it's listed in the DC directory, so entry shouldn't be a problem:

http://www.dinersclublounges.com/lou...unge-arrivals/

^^^

I should get the chance to try it out in just over a week's time. Looking forward to being able to take a shower after a red-eye TATL (seeing as the YYZ T1 Intl PP lounge doesn't have showers... T1 domestic does, though )