Flying LHR-LAX from T3 use the CX F lounge (head to Gate Lounge A) - much more peaceful than any BA lounge at LHR, and decent. Service is always with a smile, and the food offering is fine too - the dimsum are a good snack and they make noodles on request (menu on the buffet). It's not the Wing, but it's the best in T3 for OW, and in some respects better than the BA lounges in other terminals.