Suggest you speak to Stewart Peters at the Hornet Club as you are berthed fairly close by. He replaced the original plastic covered wire on my 39 with new stainless steel (no plastic covering) wire a few years ago.
If you have the plastic covered wire, I suggest you strip off a few inches where the plastic has cracked. It will be most likely be rusted and corroding away along a fair length of the guard rails. Mine was. Stewart will offer you better value than the local Gosport based riggers.