jonnymac I am afraid that Scotland is just a small Country near to London.
Population, 5.5 million, where are all the passengers going to come from to justify a new airport in the central belt?
As for the Heathrow expansion, is it not time for some joined up thinking with the half hearted HS2 being re routed to call at the airport and being redirected in the City to St Pancras International giving good connections with trains from the East of the UK, the Midlands and HS1 to the continent. Trains on the mainline from the West should also be connected to the airport so that passengers do not having to go past to Paddington to then come back out West.
Still, it is all conjecture, I am sure I will not have to worry about landing on the new third runway having only 18 years left till retirement. I would be mildly surprised if construction has even started by then.