A recurring theme of Government action on terrorism (and I don't particularly blame them for this) is that only measures that are practical and easy to implement are generally done. Extra security at airports where security is already in place is relatively easy. Walling off the back of Parliament is quite simple. Putting scanners on the tube? Well that's harder, not really practical (we have knife scanners at some stations and the police use portable ones sometimes but they are more concerned with catching feral youths than terrorists) and although it was talked about I think the government realises that they are never going to make the tube secure.
Lord Carlile is just one 'expert' who happens to have written a report which contains concerns about aviation and terrorism. I actually doubt whether the Government will pay much attention to aspects of the report relating to "lax" security at small airfields and even if they do they will soon realise that attempts to clamp down on private flying will just be impractical....the police don't have the resources and although Lord Carlile raised "concerns" I don't think he has much of an idea of what to do about them.
The police can ask private flyers to be vigilant but much more than that would fail a basic cost and practicality test so I rather doubt we have much to fear in this case...