Then there's:Oxford airport is officially "London Oxford"!
London Luton (LTN)
London City (one of the more apt names - LCY)
London Biggin Hill (BQH)
and of course London Gatwick (which also recognises the London bit in its IATA code - LGW)
and don't forget London International (YXU) - actually it is in Ontario which is a really inconvenient diversion!