I have recently replaced the belt and the heater but am know having problems with the actual drying. the machine starts and gets hot as it should, however things take much longer 2 dry and the water tanks are barly getting any water in them.
Might be the fan which is driven by the smaller belt - mine was making a row and not really going around properly. I replaced it and later the jockey wheel as the main belt got shredded. Another possibility is that fluff is blocking the airflow somewhere - I vacuum mine each time I replace a part.
There is also quite a bit of discussion on
www.ezee-fix.co.uk.
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix tumble dryers.