Hotpoint Ultima 1200 WD71 E14 problem?

I have established that E14 means a heating problem but whilst someone (somewhere!) has very helpfully left complete instructions as to how to change the thermostat I was just about to order one when I decided I would double check how difficult it was to do. Then it occurred to me how can I tell if it is the thermostat and not another part?? The tumble dryer is still getting hot so I am a little confused to say the least it seems to come up intermittently with a E30 code which I am about to check is not just a lose connection as the damn thing near takes off! Many tanks for all your help.