I have exactly the same problem, I am doing some testing with mine at the moment and I believe it to be one of the two thermostats in the heating chamber.
If you was to remove the top cover you'll find a long silver cilinder running through the middle of the unit. Looking from the front there are two modules on the left side (thermostats) with 2 wires connected to each towards the back of the dryer. These measure the temperature inside the heating chamber, on removing them the heat stays on, you have probably noticed the dryer is not even getting hot so the moisture sensor won't pick up any moisture in the air so the dryer trying to be cleaver with think the clothes inside are dry and finishes the cycle early.
I wouldn't reccomend removing these thermostats as it will probably overheat and cause a fire risk, however they should only cost a couple of ££ to replace.
Answers & Comments
I have exactly the same problem, I am doing some testing with mine at the moment and I believe it to be one of the two thermostats in the heating chamber.
If you was to remove the top cover you'll find a long silver cilinder running through the middle of the unit. Looking from the front there are two modules on the left side (thermostats) with 2 wires connected to each towards the back of the dryer. These measure the temperature inside the heating chamber, on removing them the heat stays on, you have probably noticed the dryer is not even getting hot so the moisture sensor won't pick up any moisture in the air so the dryer trying to be cleaver with think the clothes inside are dry and finishes the cycle early.
I wouldn't reccomend removing these thermostats as it will probably overheat and cause a fire risk, however they should only cost a couple of ££ to replace.
Now I've just got to try and source the parts!!
My testing has come to the conclusion its one of the two below;