Vulcan and Lightning at RAF Finningley sometime in the late 70s - awesome spectacle.
Impromptu Tornado performances in the Lake District, especially fast and low over Windermere.
Eurofighter on handling exercise while stuck in traffic near Preston.
I'm sure I saw a Spitfire / Hurricane combo as a small child but can't recall where...
But the best, by far, was the Concorde / Red Arrows down the Mall at the Golden Jubilee celebrations at the end of the long fly past.
http://www.rafmarham.co.uk/relations...s/jub-fly1.htm