How can I fix my White Knight eco86 Gas Tumble Dryer?

It starts and runs for up to 30 mins and then cuts out completely with the contents very hot, then it won't start at all for 30-60mins. During this timw pressing the activate button gets no response at all. I have checked the exhaust pipework and it is clear and i have recently cleaned out all the ducts inside. I am happy to connect/disconnect gas appliances and also to replace parts but cannot identify the cause of the problem. Any suggestions appreciated...