Right, I have a plan. I'm going to use the existing clutch cable setup with a couple of modifications. A cable adjuster (pictured) is going to be fitted at the engine end to tidy up the fitting (currently a rivnut is being used as a cable guide!).
Another cable adjuster at he pedal end allows more adjustment. I will take the existing cable and cut it down to a more reasonable size, keep the pedal bolt arrangement and solder a fitting on the end of the cable so that all the stress isn't passed sideways into the cable (if you see what I mean?). That should make it a little more reliable and gives me time to formulate a more permanent replacement when it eventually snaps!
Still no clutch arm!!!