You need to get the power on, there should be a fused spur near the unit alongside the control with a three amp fuse in it that may need checking / replacing. or a breaker or switch somewhere has been turned off that you need to hunt for and turn back on. For future reference the heating slider and the hot water slider need to be in the Auto, Once or Twice position and the setting slider has to be in the Run Programme position for the system to work. ( when you have power that is ). And I would get a room thermostat fitted if I were you. It must cost a fortune wasting expensive gas, not having one installed.