I see, thanks.
Well, I’m not an ATC professional but I was flying in that neck of the woods during that time period. I also have 14 years on the 747-400 and remember well the care we took not to stress the flaps unnecessarily.
I would answer your questions as follows:
1. London Mil.
2. I think that London Mil would have been able to coordinate a crossing of Blue One. If not, they would have handed the flight to London Control and would have given the aircraft the new frequency and maybe squawk.
3. Bedford seems like a good choice, with respect to runway length, emergency facilities, etc. In the worst case, an immobilised aircraft would be blocking the runway at a fairly quiet military field, without an active combat or operational role, instead of causing chaos at a busier civil airport. As to whether Bedford would accept them following a “Pan” call, I would have thought that they would, barring any overriding military protocol which may have existed at the time.