Had the thermostat replaced on mine by Hotpoint yesterday, and today it is still reading zero inside!
He said it will be a waste of time and he was right.
The fault is caused by the breakdown of the insulation foam behind the top half of the fridge. They can no longer fix this problem due to the usual health and safety issues!
It can be tested for by switching off and letting it warm up with the door open for a few hours. If you can push in the back of the plastic liner and feel "give", then that is is the problem - and sure enough.....
Mark
April 2011