We have no hot water coming through the taps . The water is heated by an emmersion heater but we have no hot or cold water coming through any of our hot water taps it happened suddenly.

Have you checked the shut off valve on your heater? If you have no water flow from any of your hot water taps then the problem is located in the heater cold water supply or something has blocked the hot water line coming out of the heater. First check to make sure the cold water is entering the heater and then open up a hot water tap closest to the heater. If you don't get a flow, (hot or cold) out of it then remove a areator from the nearest fixture that has one on the spout and look for trash in the screens. It's possible that a plastic dip tube in the heater has disintegrated and the particals have blocked the hot water outlet of the heater. If that's so, get back to me and I'll instruct you as to how to fix it. Good luck, Tom