As an outsider looking in, I think your government would be mad not to build RWY #3 at LHR. It's not just a hub for the U.K. or at least it wasn't. The amount of people using AMS instead over the last few years is huge. Then there's the people from BRS,BHX,EDI,GLA,LBA etc now going through DUB. Over 15% of pax crossing the Atlantic from Dublin every day originated in the U.K. and that number is growing.
If you don't innovate then you stagnate. The argument that by doing nothing and leaving LHR as it is means it won't start losing pax big time is in my view dangerous and wrong. The U.K. as a whole will lose out the longer the expansion is delayed. Other hubs are growing massively at LHR's expense. Those 80,000 direct jobs can only be protected by expansion.