I do seem to recollect seeing the mock-up at possibly Gaydon or Farnborough. However, I think it was dragged around the Midlands too as I think I saw it in a summer show in a park in Brum. I think they were allowing youngsters to sit in it as well as a Spit'. Sorry to be so vague - it's a long time ago now...
I wonder what happened to it in the end....?