Interesting discussion- we cannot however speculate on the public's interest in GA aviation without some facts to back it up.
My children can quite readily tell me if a Cessna is flying overheard or indeed a Tiger Moth. I wager that they wouldn't stand a chance of knowing what a Vulcan,Canberra or Hunter for example are if they fly over.
The vast majority of flying in the U.K is GA and airliner types - we therefore cannot choose to ignore or indeed presume that there isn't an interest in them. I am a great believer in 'setting out your stall ' and then letting the public decide themselves.
For example the Turbulent at the Midland Air Museum stands next to a Flettner helicopter frame which is of great historical importance to rotor flight. I bet far more members of the public show a interest in the Turbulent purely because of it's looks
and the fact that they can relate to it.
The presentation of light aviation is what is needed - make things bright and fun and people will show an interest - tuck things in dark corners under military aircraft and the public will naturally look away.