No it isn't. The fact that the final connection to the immersion heater can be in the hot press is simply for the reason that it cannot be anywhere else as that is where the hot water cylinder is. Furthermore the connection will be in heat resistant (e.g. butyl) flex. The actual switch/isolator is prohibited to be in the hot press.Well, for a start, if it is (as it must be) acceptable to have the final wiring to an immersion heater in such a place, then it's hard to see why other wiring (if properly designed) should not be equally acceptable.