Thanks both for the feedback. My connection time is just under 4 hours at the moment, and I don't have to check a bag but would like to if I can. Suppose will see how much schedule changes affect the itineraries as we get closer to the September departure.

Ironically the last time I flew through LHR in I was on one long itinerary, SMF-PHX-LHR-GVA with the PHX-LHR leg on BA metal, and they lost my one checked bag (this was in the midst of the Summer '22 Heathrow meltdown) Turned up at my home airport unannounced 3 months later.