I think you're all being too parochial. Come on, let's think out of the box! Why let distance from London and lack of transport links limit who can call themselves "London Airport"? From the Beeb article:
Distance to London Airports
- London City nine miles (15km)
- London Heathrow 18 miles (29km)
- London Gatwick 30 miles (48km)
- London Luton 34 miles (55km)
- London Stansted 38 miles (61km)
- London Southend 43 miles (69km)
- London Oxford 62 miles (100km)
- London Ashford (aka Lydd) 73 miles (117km)
(Source: Google Maps - shortest route starting from Parliament Square)
What's wrong with London Insch? (Aberdeenshire, 554 miles or 886km driving distance from Parliament Square.)