Qwertyplop
I have to disagree with you, as you appear to be rather naive about the proposal.
I fly a very small aircraft that can carry me, fuel and a GPS, If I hit a building, I will be sitting (dead) in a pile of matchwood having bounced off the structure.
Compare this with a Cherokee jeep driving through a doorway at an airport. In fact there are a number of model aircraft that are bigger than my little aircraft and a bomber wouldn't even need to risk his own life to wreck anything
Similarly, if I were to try to blow up anything worthwhile, I would use a SAM missile at any point between Southwark to Heathrow or Heathrow to Windsor.
GA of my sort is not an effective threat in any conceivable way. Someone wanting to fly out of a farm strip would have to have completed the NPPL at least and then worked on strip flying for a bit - that is not the way that terrorists work.
They use low-tech tecniques and do it in the easiest possible way - forget about low end-GA. It is yet another scare story from a government who needs to keep us worried.