Forget about London airports
Know this may be a little out of the hat for most, and it is a comment as a northerner, (Ey up lad, where's me flat cap!!) but instead of focusing in the south east why can we not have a Central UK airport? All we need is an area with a slightly quiet airport operating already, that is in plenty of open space, with a major motorway links on its doorstep, connected to Kings cross via a HS rail link. My personal view is a development of East Midlands with another runway etc would be a more common sensical move, SID and STAR with so little overfly and clean routes to both the Atlantic and Europe.