Leisure Zenith 55 Ignition fault? Cont?

Re: Leisure Zenith 55 Ignition fault? Feb 2009

Thanks Tony S. Have tried most of these but still got a problem!

The oven control knob has an S on it and when lighting the oven one would turn the knob to the S position and push the knob in until the oven lights and then chose the temp.
Could the switch be sticking ON after the knob has been released and how can I check for this?
Cheers.