True Blue,
Re LGW and LHR post.
I see 3 advantages at work here. Ability to make a connection on the same ticket ( as opposed to booking separate tickets or using low cost airlines). The scale of the alliances helps too, with all being well represented.
The catchment around LHR is huge in West London and makes LHR an attractive choice.
Having the tube is a plus, eventhough not any faster to central London than LGW (slower in the main), but attractive price wise. Though on.the while train ticket price only a part of it!