Flying MCO-BEY via IAD and LHR on UA and BD. I managed to get an upgrade from eco to business on the MCO-IAD-LHR on UA using miles--I was wondering if I would be able to use the Arrivals Lounge in LHR. I have about a 3 hour wait and I would like to shower and take care of some things. I usually fly into LHR's Terminal 3 and pay the fee for the No1 Lounge but flying UA and BD this time, it looks like I am flying in and out of terminal 1.
I can't seem to get a clear answer--thanks for the help.