RAF St Mawgan's airfield site has been sold off to the county council but having said that, given the low volume of civilian flights I don't think there's anything to say that the RAF couldn't share it? (Given they often drop in now) The old Nimrod hangers are being used privately now for the Classic Air Force and other private things I believe, but I think there would be plenty of space to build new ones inside the wire next to the HAS site