Thank you for your reply.
After a bit of searching I have managed to find the part required. It's (as you state) the thermal cut out. I have ordered it from partsmaster for £37 with next day delivery.Fitting it is as easy as pulling off the old connectors (remembering where they go) and pushing on the new ones attached to the new thermal cut out.
It seems to be a common problem and could save you a lot of money by DIY (DON'T FORGET TO ISOLATE FIRST).
Cheers
Boasey
February 2009