It's probably the thermister kit needs replacing. http://www.espares.co.uk/parts/tumble-dryers/hotpoint/ctd00p/p/1088/808/0/511141?k=thermostat £19.99. Access from the back. I replaced mine on a different model in 10 minutes saved a fortune. Not soldering it's spade connectors. Just need a philips screw driver and long nose pliers. Watch out for the metal edges on the back panel as they're sharp.
Jason P, October 2009