Originally Posted by
Time traveller
As a OW Emerald, you should be able to use the Galleries First lounges at LHR if flying on BA or any other OW carrier.
This is correct. As long as you are flying a OW carrier, you can get access to the premium lounges of the OW carriers are LHR. In BA's T5, go to the south lounge area and enter the First lounge (there is a Business lounge there as well. Go to the First lounge, it's quite nice).
As a OneWorld Emerald, I always carry my elite status card (in my case my American EXP card) which reflects my emerald status. I show that card along with my BP to enter the lounge.
If you find yourself in T3, there are a number of OW lounges to my memory: BA (Business and First), AA (Admirals Club and Flagship lounge), CX (Business and First) and I presume Qantas though I have never been to that lounge.