Re:
Next problem the bottom bracket, a strange FAG design with plastic lock rings either side. These had gone very brittle and a normal lock ring spanner just chipped bits off. A pair of mole grips took off the left side in seconds but the drive side was stuck solid.
I used a grinder to cut spanner flats into the plastic which gave a really nice hold, but no good it was still stuck solid. Eventually the remaining plastic sheared off, leaving nothing to hold at all!
Nothing for it, I used a thin drill bit to chain-drill the plastic between the shell and the metal bearing race. Miraculously I didn’t damage the shell threads with the drill but somehow managed to scratch the threads on the other side when I pushed the bearing race out! A quick go over with a thread-restoring file soon sorted that (get one if you don’t have one, very useful and often all you need rather than a full tap. I tend to use it on even new frames, amazing what a difference it makes installing). A quick check and the new cups went most of the way in by hand.
The old BB: