I removed the horrid ball head toilet from the boat and I have now blocked up the hole. Having used a disc sander to clean around the hole on the outside I put a patch of 3 layers of glass fibre matt soaked in epoxy and held them to the hull with a plastic disc held in place with a piece of wood and a brace. I then went inside the boat and put more epoxy resin and chopped glass matt in the hole as well as a wooden plug. I then put more epoxy on top...no water getting in here!
It just needs a final sand and then it can be primed for the antifoul but that is still al while off.