Hi Col,
I did this recently and if you want to replace that rubber buffer you have to disconnect the cable at the front of the car and take the handbrake lever out.
There is a guide pin on the top of the rod with the notches for the ratchet. This pin will stop you fully withdrawing the rod which you will have to do to replace the rubber piece. The guide pin is an interference fit and you can drive it out by lining up the pin with a hole in the underside of the tube. The hole is made for this purpose. Mine took a real beating before it came out hence why you have to take the lever out !
It's all time consuming but do-able. See the pic. Anymore questions, just ask.
Peter