An update on this problem.
What had happened was that a wire connecting to the fan, which circulates the air when tumble drying, had come loose. This meant that the air didn't circulate and the element overheated. The 2 Thermal Overload Cutout (TOC) devices did their job and stopped the power getting to the element. All that it needed was 2 new TOCs and the wire to be reconnected.
Andrew
November 2006