Originally Posted by WineCountryUA

The issue at both EWR and LHR is flying VS is you are flying out of different terminals than UA (and where its lounges are located)

While in EWR, it appears VS and UA are both in Terminal B, Terminal B is actually 3 separate terminals with three separate security access and UA uses Term B mostly for International arrivals and a few overflow flights -- the departure activity is small.

At LHR VS is in a terminal far away from the UA gates / lounges.

So, in theory until November, you have access but in practice, it is not very practical.