In reply to Pj84:
OK.
Cam repair summary (and my pension hobby gone as a gift to the world).
Remove old wire - both the flexible bit (that has probably frayed) and the solid bit that goes into the cams.
Cut an 8" length of strimmer cord and fold one end over about 1cm from the end. Pinch it either with pliers or your teeth. Then, and tis is the delicate bit, you need to cook the bend a little. You can do this with a gas hob, a candle, a lighter or, best but not found in every household, one of those butane guns that you use for creme brulee (can't do the accents, sorry (except for posh, obviously)). Thread the cable throuh the trigger and even up. Then put the short, bent end through a lobe and trim so that it stands perhaps 2mm proud. Heat a knife end or other bit of metal until it glows and gently flatten the protruding part. It will forma flat blob that is more than enough to stop the cable pulling through the lobe.
Now thread the other end through the other lobe and adjust so that the trigger allows the cams to rest on stops, but no more. Mark where the bend needs to be with felt-tip and repeat the whole process.
Finally, do the whole monty on the other side.
To be honest, once you've done a couple they are excellent... and last forever.
Why don't Wild Country just fit strimmer cord to start with rather than that ridiculous wire cable with the string core?