Why isn't my White Knight 797R dryer heating up?

I have a White Knight 797R tumble dryer which has stopped heating up. It does all the correct noises and the drum rotates as though its working ok, but even after 10 mins running, its still lukewarm / cold when you open it up. Admittedly, the fluff container was a bit choked up when I looked so this may have caused a problem. I have looked on this website and others have mentioned a red button at the back - I've looked - this model doesn't have a red button anywhere on the back. It could be a sensor, but I haven't a clue where it'd be, or even what it'd look like if I went searching for it.

Does anyone know anything about these machines and how to fix them.

Many Thanks

Nigel.