Early Departure at Heathrow T2
I have a Lufthansa flight tomorrow morning, departing at 6:30am from T2 in LHR. I'm currently staying near Paddington station and came over on the Express, however it appears that the first Express back doesn't leave until after 5:00am. This would get me into the station at 5:15 and likely not back into the terminal until close to 5:30 which seems incredibly risky. There is a 4:42 train that arrives at 5:04 which is a bit better, but still only 75-80 minutes before flight time.
Do I have to clear passport control outbound (US passport)? How much time can I expect in queues at that time of morning in T2? I have one bag to check, but I'm Star Alliance gold, so check-in shouldn't be too much of a problem.
Thanks in advance.