Hi Jacki,
Log on to 'www.partmaster.co.uk' and click the Cannon trade mark symbol.
If you dont know the actual model number, click on the right hand cooker picture (20155E) then on the new page click on the word THERMOSTAT in the blue 'refine search box' You can now take your pick from 4 types of thermostat pictures which you can probably match to yours.
Of course if you know the model number you can enter it into the search box. Voila!
Cledlyn
August 2008