I had a similar problem, which turned out to be the heater relay on the main board.
This had fused in the on position, which resulted in the heater running when the door was closed, whether the machine was running or not.
The build up of heat blew the one-shot thermostat.
The main board (I thing hotpoint refer to it as the drying unit) is about £120.
However, if you're good with a multimeter and a soldering iron, you can test the relay, and replace it.
From faint recollection there are 3 large orange relays on the board, one is rated at 16A, the others less.
I think the heater is the largest one, rated at 16A.
I sourced a matching component from Farnell components for a few pounds. ( I think their min order is £10, but I also bought some batteries.)
Barry, October 2009