I've just had this problem too. Dryer would run for 5 mins then stop, the only way to run it was to hold the start button in.
Changed the thermostat kit first (hotpoint part number 1701583) but still had the same fault. The problem turned out to be the start relay, got one from sparecentre.com (again a hotpoint spare part number 1701157).
Garry
January 2007