Not hot water from Pulsacoil 2000

The water is not heating up correctly , we think it might an issue with the thermostat.. at the moment we have no hot water and have tried the old trick of turning the system off and then back on after 30 seconds ... it does not want to know . we have also tried using the boost function and this sounds like it is going to work but then we have no hot water please can anyone help ....
No plumbers in Southampton want to know when we mention the systems name.

Is the unit getting hot when on boost?

If the unit is becoming hot with the boost and (or) the off peak supply, then the problem could be with the PCB, Pump or sensor. Also check the water level in the header tank and make sure the main unit is always left on.