Hi, I just had exactly the same problem and fitted the following part myself; http://www.espares.co.uk/part/tumble-dryers/hotpoint/p/1088/808/0/0/1020444/washing-machine-%2f-tumble-.html
They were pretty easy to fit (just need to remove the cover at the back of the machine and 15 or so screws) and cost only £6.99 plus postage so you could save yourself £30 quid on calling a someone out!!
Dave
December 2008
Just had thermostat replaced on my tumble dryer and sorted the problem. Job carried out by a local repairer for under £40
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix tumble dryers.