Hey Nick,
I didn't know that trick regarding the BTR-2 top plate dimension, thanks
I've seen reports that the BBC bought something like 500 of these machines from EMI through the years although, who knows? They certainly had a lot of them.
Anyway, I'm guessing you've logged quite a few air miles on them yourself yes?
Edit: thanks for posting a higher resolution of the 'room 51' Abbey Road pic.