Re: Tumble dryer, no heat.
You need access to a meggar or multimeter and know how to use one.
If you do then remove the mains plug, take off the small back panel and test the two small thermostats above the heater. They should not be O/C.
Reasons for failure, age, failure to keep the condensor clean, opening the door whilst machine is still hot, capacitor failure etc.
Thermostat kit is HERE
Handle the new ones with care, do not put any pressure on the base of the new stats.