V-Flyer

I am flying UCS LHR to SFO and then onto LAX with American West (not first class). When I am in transit would I be allowed to use the virgin lounge?

Short answer, no. The Clubhouse is for departing passengers only. In any case the America West flight is from a different terminal at SFO and you will need to go and check in and clear security, I guess.

BC

As BC says, the CH is strictly a Departure Lounge for VS pax departing on VS020 only. Best option would be to pay for lounge access through one of the various programs or use a Priority Pass lounge if you have membership.