how to fix my storage heater?

It sounds as though you have tripped the safety cut out.
Make sure the heater is switched off at the spur on the wall, take the front panel off (either 2 bolts at the bottom if the model is an XL, or 3 screws at the top by the wall if the model is an XT).
At the top right of the heater, you will see the input control (The bit you turn to make it hotter / colder). If the model is an XT there will be a black disc with a white knob in the centre. Press the white knob and it should click. If the model is an XL, the input control will have a little red box that has what looks like a wire sticking up. Press that down and you should hear a click. This should hopefully sort your problem

Kind regards
Cowans Heating

Cowans Heating
March 2007