I have now removed the points, condenser, springs, weights and cam plate and de-greased the unit as best as possible without actually removing the distributor from the crankcase.
I mentioned earlier about some 'scoring' on the underside of the weights. It look like the 4 raised rounded areas, as can be seen in the photo, may be the cause but I think they are there to reduce friction for movement of the weights, so it may be normal to see some markings.
The components, in my inexperienced opinion, look in good condition but I have two questions, perhaps silly ones...
1) There is a screw which goes in the top of the rotor shaft, which I thought was there to secure the cam to the shaft, but it does nothing. What is it for as it doesn't secure the cam in any way unless I have a missing part !
2) I have not removed the distributor from the crankcase. Can I assume that the ignition timing will not be affected by what I have done so far ?
Thanks all.