Before the new year I noticed the clutch return spring had almost worn its way through the clutch arm anchor. A new anchor along with the spring, pin and split pin was ordered.
After changing each piece (just after Christmas) the clutch refused to work and would only crunch into gear (the mechanical sympathy was high!).
I came to the conclusion that the new spring was very strong and must have been putting too much pressure on either the master cylinder or the slave cylinder.
Instead of replacing each part separately to find the cause, I ordered everything for the hydraulic system. After replacing everything and topping off the master cylinder, the clutch returned.
And now works better than before, happy days! (No spring on anchor in photo, fitted after photo was taken)