Mine is an Alpine head with the double-Din panel. That one has definitely never needed the code, I don't have it anyway.
As far as I know, the rest of the range are the same, but you'd need to read the ICE Handbook that comes with the car, if you haven't got that, check online having first identified which head unit you have.
Peter
I have this unit my disco (not sure about the jack plug though). The battery was disconnected and it is now asking for the code which I don't have. I read somewhere that the code is the last 4 digits of some sort of serial number within the car. Can anyone confirm this? If not who do I need to get in contact with to get the code? Cheers, Danny.