The module waits for the water to get to the correct temp before moving on,If the heater has stopped heating then it will wash forever ( except if cold wash has been selected ). Could get F08/F07 .It could also keep washing it the drain hose is pushed all the way down the stand pipe ( just allow 6 inches of the drain hose to go into the pipe ). Check this first .

This is the heater . When the heater is tightened the rubber (arrowed) is squashed and it makes a water tight seal.When the heater has been in a while, the seal becomes moulded to the drum and makes it hard to remove .

When the heater fails it will either trip the electric or wash forever ( it waits for the correct temperature before moving on , because the heater is not heating it will never reach correct temperature )

The best way of checking it is with a multimeter.Check while still in machine.Remove the rear access panel and disconnect the wires at either side of the heater (take a photo of the wires so that you know where they go if any problems).

Select ohms (the horse shoe symbol) connect the meter leads and the reading should be about 30 ahms.

If it trips the electric then disconnect the wires at either side of the heater( and isolate (wrap in pvc tape )then try it again if it still trips then you are looking in the wrong place.If it doesn`t trip then change the heater.

To remove the heater take off the wires and unscrew the nut.With the nut removed the ntc can be withdrawn complete with wiring.

The heater is removed by prising it with a screwdriver or similar tool , It can be a right pain to remove.Get some long nose pliers and try to grab the rubber seal, try to prise the heater out square as there is a fixing lug inside the drum .

Here we can see the heater loose .

Here you can just see the heater locator inside the drum, this is where the heater sits .Very straight forward to refit.