Why not make use of the perfectly good underused airport with a long runway, at Manston in Kent? EUJet flew out of there until it went bust, and it still has charter flights and occasional other scheduled flights. The high speed train from St Pancras has a link into the north Kent towns via Ashford. Manston airport is already there - it's the one a lot of relief freight flights leave from, so why build anything new? Lydd airport is also about to be redeveloped down on the south Kent coast, but that has hardly any rail links at all at the moment (I'm sure it will in due course!)