I was there also. Right on the flightline and also felt the blast wave of hot air from the explosion.
As he pulled up into and over the top of the loop, it was obvious that the circle would not be big enough to avoid the ground and a few people around me just said "oh no".
A trully shocking thing to happen. What was particularly upsetting was the air show commentator had been going on during the display about how he and the pilot were old mates and were going out for a pint together later that evening etc,etc. When the crash happend he tried to carry on with the emergancy announcements about "please let the crash crews through and dont approach the crash" in a clearly distressed voice until someone else took over.
I also recall the Russian pilots and * seem * to remember they had been taxying out in the distance when the spitfire was displaying and then after a short delay they took off and did their routine ? (is that right ?)