It was a stunt just so they could have the FFX on the track because they can only be driven by the owners and Schumacher was willing to lend his skills and car.
Did you really think that during his busy F1 schedule Schumi would hop on a plane to Brittain to do a lap and then fly back?
There's like one main stig, and there are special appearence stiggy's that do crazy stuff like ride a snowmobile of a skijump.
If you google you can easily find the name of the main stig I will not post it here tough.
I am a part of all that I have met. ~Alfred Lord Tennyson