@ Pete, I'm up north on the doorstep of the lakes and thanks for that link.
@ Patrick, I've removed the film back, the focusing hood and the bayonet lens, the only thing I cannot shift is the helicoid lens mount, which seems to be jammed and the release button is doing nothing. The loose screw is like something you'd see in a wrist watch, and was lying on some black cloth at the base of the camera! There is no way of me fixing it, it needs precision tools and skills that go with them to sort it out now. Time to make some phone calls...