I reckon the heater element has busted, so the question is; How easy is it to replace with a new one ?
Spares seem to widely available at around £20.
I'm guessing that the job entails accessing the element mounting from the rear of the machine and probably involves unplugging the electric leads, removing two or three retaining screws and simply withdrawing the old element - then reversing this process with the new element.
You are more or less right. Off with the power supply and unplug at the wall. Disconnect the water supply and lower the waste pipe to the floor and drain it onto a towel until its empty. You may well have to access the element from below. Would recommend taking a photo of the wiring before you start to remove anything. You will find the element has a couple of chunky pipe clips holding water pipes to it, and a few screws holding the element case to the frame.
It's really just a fitting job