Why not check in the manual? If you don't have it, a copy should be really easy to find online.
This took me less tan 30 seconds:
http://www.gotogasdocs.co.uk/f/m/Cannon/Cookers/Chichester%20Before%202005%20IUM.pdf
I doubt the ignition is battery powered. Why would it have a battery powered ignition and a mains powered clock?
Maybe the ignition module is u/s or possibly the ignition switch.
Can you manage to look for spares yourself?
XXX, January 2017
