Wow this lounge thing is complicated! lol I'm flying from LHR-SFO-SEA (Global First on initial leg then United First on the domestic leg) I have a 6 hour wait between arrival in SFO and departure to SEA. Will I be able to use the International First Class lounges at both Heathrow and SFO? This is all on one Mileage Plus award ticket. Any tricks or advice I need to know? Thank you very much!