Hi Duncan
It may seem simple, but there are one or 2 things you can check before going nuts!
First check the lint trap is clean, this is inside the door on the bottom and pulls up and out, you will be amazed how dirty this gets, secondly check the condenser, pull down the bottom flap under the door and on the left is the condenser, undo the 3 tags and slide it out, give it a good wash under the tap, again it will be full of lint! Lastly have you checked the heat setting button on the front? If it is pushed in you are on half heat, easy to do, I've done it myself.
It would seem unlikely it is anything more major, if the thermal cutout has operated then it will not work at all and if the heater element is broken, it would also not warm at all.
Hope this helps.
Richard, January 2008