Lindy,
You’ll have to come up with the model number at least and preferably the serial number as well to let DC try and solve this for you. Check the user book for the model number, failing that it will be on a rating plate on the underside of the hob.
DO NOT try and lift it – it will be attatched to a rigid copper pipe, peek underneath if you can.
Failing that, get the pros in – you don’t want to make ANY mistakes with gas. You can check in the Directories for a local UKW engineer, or, put your postcode up in here and someone will pick up on it.
Regards,
Penguin45.