Sticking plaster approach is what the UK seems to do with regard to any transport problem and has been doing so for the last 50 years.
Proper hubs are on mainland EU and are well established. A new runway / terminal wherever will not compensate for that business that is long gone. LHR is stiill poor for ground transportation and we need fast connections to the EU by rail, even that prospect is a long way off, as there is little or no rail capacity left from LHR or anywhere else into the London terminals.
Any major runway / airport build can only be funded by government and would have to be written off. Is that not the reason for airline amalgamations thus to ensure that where you fly to and on which ever airline they all share the pot. In the end it does matter in which country the main hubs are.
I recall as many of you will the push by BA to get KLM and thus get the Dutch hub which is perfect for dispersal by ground transport within the EU, apart from the UK.
I fear it will require more than a change of Uk government to get any improvement. Surely the push for T5 had more to do with the desperate need to bulldoze T 1 2 which were so far past there sell by date. T 3 and 4 are fast approaching that and new frontage has done little to improve them.