Creda Storage Heater, thermal links blowing continuously!?

We have a Creda TSR storage heater in the living room and last winter it stopped working! I opened it up last month and found that the 'thermal link' which I think acts as a fuse had seperated/blown. Bought a new thermal link and fitted it last week, came downstairs the next morning hoping to feel some well needed warmth and it was still cold. When I opened it up the brand new one had blown also!! I wonder what is causing this?

Here is a link to what the thermal link looks like when new:
http://www.torreelectrics.co.uk/acat...use_links.html
(2nd picture down)