This boiler is the Qualtex MIS884 35L 2500W sold on ebay by LM Electrical, or 4YourHomeUK or ApplianceSparesWarehouse websites. All 3 are the same owner as Qualtex.
Just posting the model number so people can find this info on it when searching. There are other models too:
MIS882 9L 1500W
MIS883 20L 1500W
Here is some useful info from the manual:
To prevent accident from boil-dry, the appliance is protected with a thermal limiter. If water in the tank is boiled dry, the limiter activates and the appliance turns itself off, although the lamp will remain on. If the thermal limiter is activated, there is a manual reset button located in the middle of the base bottom. Turn off unit. Let to cool. Press button to reset.
The heating element is fitted with a thermal cut-out,which protects the urn from damage when continuous misuse of the urn is allowed [boil dry, switchedon without water, or the appliance exterior has been accessible with water) the thermal cut-out will stop the appliance from working. Do not confuse thermal cut-out with boil-dry protection. Thermal cut-out in the appliance isa disposable part.
The manual also has a circuit diagram with a fuse icon but named FESR, and 125 and 92 degree switches.