This might help - relates to a Cannon Camberley cooker
Can't claim the credit for this but this earlier post by Kash says:
I have the same cooker and all i did was switch it off at the mains and when it come back on the timer display showed 24hr,just set time by pressing select button and the the + or - and oven started working again
kash
April 2007
Chicks Fan
December 2008