Keeps losing heat and constantly have to reset using the button on the rear of the apliance.

Alan M., October 2012

The inside of the casing is probably bunged up with fluff causing a reduction in the output of the fan which in turn is causing the safety overheat switch to trip out.
Unplug-take the back off- get vacuum cleaner - have a field day removing all that fluffy stuff, particularly round the main motor and fan.

Geoff inside Wales, October 2012