Hi Dave, have you tried a slinky glide cable from wemoto yet? It's a very decent pattern cable, so worth a punt.
Will have a look. Remember reading about a guy with an old
er British bike that he had bought new who was on a run with the air cooled rd club, his clutch cable broke! Cannot remember the bikes age but had something like 57,000 thousand miles on it! Could live with that! My bike shows 9,650 and the cable is about half way to breaking at the handlebar lever end! Only reason I can think of is the cable is as dry as a nuns crotch!