Earliest I remember was either Biggin Hill (late 80's) where my only real memories are of a French Navy Super Frelon taking off rather close to us from the static park and blowing dust into my eye. Those things are huge but from an eight year old's perspecive they're like VTOL 747s! Of course I cant forget the Vulcan that day.
Apart from that, around the same time was Alconbury (although I think that was 1991) watching a display by the USAFE. Very low cloudbase I seem to remember. Best thing was the Herc with the Fulton arms (is that right) that picked up downed pilots. U-2, A-10s etc.