The public purse has to learn to live within it's means, something no politician in recent years has contemplated. The answer is always "tax more".
On the contrary, recent governments, including the current UK government, have taxed less and borrowed more. Greece is a prime example of where such policies lead. Does nobody who thinks UK Income Tax rates are too high remember the days when we mostly accepted without too much objection a basic rate of 7/9d (about 39p) in the pound?
But back to Heathrow. As a transfer passenger, I never like having to change airports to make a connection. I care a lot less where exactly the intermediate city might be. so, somewhat reluctantly, I would support a third runway. However, if the demand for new routes to economic hot spots is really there, why not offload some of the services from routes with multiple fligts per day to a secondary hub in MAN or EDI? BA could surely fill one of the current JFK services from MAN, and use the vacated slot to initiate a service to somewhere new, like Seoul.