I can understand quite well the attractions of Lhr. Lhr has almost monopoly power now for the reasons you state, airlines want to move there. In the process, keep Lgw from becoming a competitor and in turn, you are able to push up prices due supply and demand. He presto, everyone wins except the paying passenger, that is you and me. So it is in the interests of most of the travel industry to convince us that Lhr is the best option for everything and with that happening, make Lhr even more appealing for airlines. It is revealing that the recent report states that Lhr will only provide 2/3 new destinations more than an expanded Lgw could provide. Yet the tone of that report is that Lhr is far and away the best option. For who? Because as I see it, support for an expanded Lhr means higher fares for all of us who have to use it. That is the way the providers have it now and want it to stay.
TB