I'm at the other end of the UK, and have a strange detachment from this discussion.
LHR may be the only Hub airport in the UK, but it is not the Hub airport for the large majority of the country. Even after R3 is built, only 14 UK airports will have links to it. At the present time, 26 have flights to AMS, which has become, de facto, our hub. Maybe this should never have happened, but it has. The ship has sailed.
The enlargement of LHR is not a National project, as I can't see how it will benefit anyone outside its local catchment area in the south.