Easy to do. I followed Ash's instructions with just a slight variation.
I first filed a flat on the coil above the lead and then used a sharp chisel to gouge out the plastic above the lead. I kept digging until all the lead was exposed right back to the metal pillar to which the lead is attached. A Dremel with various burrs helps. I removed the old lead completely. You should now have a trough into which the new lead will be inserted. I then drilled a 1.5mm hole in the pillar. I used new silicone leads into which I inserted a short length of 1.5mm copper wire into one end leaving about 15mm protruding from the end, this is then inserted into the pillar and soldered up with the lead fitting snugly in the trough. A bit of araldite to seal the join and leave to set. I left mine overnight. Then I used black Milliput to finally seal in the lead and once set filed to the original shape.
Eric