Creda TSR Storage Heaters?

I bought two TSR Storage heaters on 22 December 2009l they lasted 3 weeks before they broke. The company I got them from replaced them immediately, the new ones lasted a week before they broke again.

Creda are less than helpful, that is, when you can get through to them. The flaps on the contol panels melted when they did work.

EDF Energy have been out twice to check there is power getting through, and there is.

Any assistance or advice you can give, would be greatly appreciated.
thank you
Fiona