I certainly did not see a black glider like thing outside the 51 sqn hangar ay Wyton in the early 1990's one night. I didnt see a bloke in a space suit emerge from it either. Never asked and still cant figure out why it was there as Alconbury was just down the road.
I came over to Wyton the next day to assist with recovery of that plane.
The reason that it diverted to Wyton was simply because of crosswinds outside of safe limits at Alconbury. Not sure of the angular relationship of the Wyton runway versus that at Alconbury but that was the reason that it stopped off there rather than coming back home.