the trips in the tumble dryer have a disc , and when they trip they go from flat or convex to concave, if they are gone concave , remove it / them one at a time , sometimes one screw sometimes two, take off the two wire spade's, hold the trip between thumb and two fingers , with concave side faceing down give a sharp tap on a hard surface (worktop will do when the wife isen't looking)if you hit it hard enough it will reset the trip replace and it should work again, this fix may not last long, could be five min half hour week, mine has lasted three + years , you must find the reason for the trip, blocked filter, fluff in the air system that caused the heat buildup that caused the trip in the first place, the trips can be had from rs components at a fraction of the price , hotpoint £18 quid as about £4 +pp from rs
"above all unplug the machine befire doning any repairs" wrap the plug in a plastic bag or sum such to avoid accidents. hope you find this helpfull.
NED, August 2010