Piezo gas igniter?

My Cannon Chester (model 10545G) gas cooker has developed a fault with the electric igniter to the gas rings and oven burners. Although it ignites each of these elements satisfactorily it continues to click for some time after the flame appears. Can you help.Which part would you suggest needs replacing?
Thanking you in anticipation,, I am.
Yours faithfully, J.K.Booth