Thanks to the clutch cable being badly adjusted (another corner cut Chris and Mucker) the old clutch gradually wore away and cost me £500 to replace. I spent about an hour today with a drill and a couple of spanners and set it up properly.
At one point I had released the tension on the cable and discovered the lever that attaches to the clutch was loose and rattling around. A phone call to Arthur the clutch man reassured me that it was normal and I soon had it back in place.
There were two positions for the pedal end of the cable retainer, one too loose and one too tight. I drilled a hole in between them and with a few little tweaks it was perfect.
The kit I bought on eBay was unnecessary after all but I'll keep it just in case.