Sorted my problem where my white knight dryer stopped before the clothes were dry (a bit more than damp), maybe it's the same for you. In addition to the two sensors on the back of the machine, if you remove the top cover and look at the top of the drum, there is an additional sensor (attached to the circuit board by a red wire) which pushes down on the metal sleeve which wraps around the drum.
When new, it looks like this
http://shop.ukwhitegoods.co.uk/Tumble+Dryer+Parts/White+Knight/Carbon+Brushes/421307845022+-+White+Knight+Tumble+Dryer+Sensor+Brush.html
My one had worn down so that only the spring remained. I ordered the above, replaced it in the machine, and all works again.
Hope this helps
Nigel.
Nigel, November 2008