Hi Bob,
Some of the thermostats can be reset, the left hand thermostat on top of the heater box sometimes has a little hole in the middle of it, if yours has then push a thin nail or pin down the hole untill you hear a click. That stat is now reset but if you cannot reset it then they can be purchased from this link below.
http://www.candmdomesticappliances.co.uk/product.php/306/0/thermostat-kit-green-spot-creda-1701583
www.candmdomesticappliances.co.uk, January 2010