Richard, the ignition key number is not the same thing as the 4 digit code needed for reprogramming the keys into the roof receiver, hence my frustration as i don't have the 4 digit code to get the central locking working from my fob again. I think it's just a number that will allow another key to be cut if you end up loosing both your keys. The immoberliser number will allow you to carry out the imergency start up of your car if the thing ***** up. I obtained the codes from Mangoletsi in Knutsford who were helpful to me as oppose to other dealers who didn't want to know. Are you having the same trouble as me, ie key fobs stopped working the central locking.