And, on planning and certain other matters: The General Aviation Awareness Council
"The GAAC is the most representative UK body in General Aviation and is recognised as such by Government, the CAA and others to be the organisation that speaks for General Aviation on planning and environmental issues and we intend to widen our ‘awareness’ campaign to other issues where there is consensus."
(AOPA is a member of this one – in fact one of the founding member associations.)
The General Aviation Awareness Council
Chris N.