It is very common for Tumble Dryers to fail in this way and it is normally their Thermostats that are the cause. They are very easy to replace and buying them from the internet is easy too. Normally a pair of Thermostats cost around £20 (you replace them in pairs).
There aren't many parts on a tumble dryer so dismantling them is straightforward... don't be afraid to try!
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix washing machines.