I have tried all sorts of silicone eaters, all of which claim that you just daub on, leave for a while and remove all traces. All of these products lie!!! The only way is by the skilled use of a very sharp blade. I find a No 22 scalpel blade in a No 4 handle and a No 10 blade in a No 3 handle...
Hi, just in case it's of any use to anyone in future, the instructions in the Potterton manual for removing the diverter valve are not quite correct: the lower CH flow pipe must be disconnected before yanking it out...