Haha, I have been spotted here and there...
Here's a pic of it from 1977, incase you're wondering on what it looks like... It still has the original tyres on it!
http://homepage.ntlworld.com/nkilgar...7/Majestic.jpg
As far as the bottom bracket is concerned, I think the threads in the frame have seen better days. I say this as it took lots of elbow grease to get the BB cups out. I managed to do the non-drive side with a plumbers wrench, but the drive side needed a 35mm spanner. I had to stand on the spanner because it was so tight.. but it also needed lots of effort to turn the spanner once it had been loosened, so the threads must be tight.
The BB definately British thread, as I had to turn the drive side cup clockwise to undo it. Now on the exellent sheldon brown site you linked, there seems to be two sizes of thredind for the threading for the British standard...
1.370" X 24 tpi
1.375" X 24 tpi
Very confusing... Only the British could come up with one standard with 2 different thread sizes.
Perhaps that's why my shimano BB that I tried didn't fit? Perhaps the shimano had a 1.375" thread while my frame has 1.370" threading... So where on earth could I get a correctly sized BB? If not, maybe a new spindle and balls and ball cups would be ok, as the existing cups fit ok, if a little tight.