My clutch replacement was successful and the spigot bearing and seal were the correct sizes so details are:
Bearing - 6200 2RS C3 ball bearing - the C3 is important because it denotes larger internal clearance for higher temperature applications
Seal - 80mm x 100mm x 10mm R23
Interestingly, as well as the spigot bearing being sealed the garage reported that the clutch plate was stuck to the flywheel when they took it off. I was badly stuck when I finally got the engine running but never really sorted itself despite driving it 800 miles before it went to the garage. The car is massively better to drive now!