UAPremExecflyer: Thanks for the reference to the other threads. I had not realized that I would have to lug my check-in luggage as well. With that and with what Nuhusky wrote (US passport), it appears that the bottlenecks (not necessarily in that order) would be:
- time to wait for checked bag to show up in LGW
- immigration clearance
- road bottleneck (if taking direct bus, which is best option with checked bag)
- security at Heathrow
- anything else?
I noticed that there is an earlier flight available the previous day which gives me over four and a half hours of time to switch airports. That appears to be a better bet. Maybe get trip insurance as well...