Hotpoint Tumble dryer shorts my house trip switch!?

I have a Hotpoint condenser dryer which trips the mains trip switch every time I try to turn it on. I think the timer switch on the dryer is broken, but am not sure so I don't really want to fork out £40 for a new switch if it turns out not to be the problem. Anyone got any ideas how I can test the switch or the rest of the electrics in the dryer?