Is it the original vauxhal radio in it, Go to vauxhal dealer with it and they will (should) have the car on there computer which should in turn have the stereo serial number on it with this they can give you the code, they will probably charge you for this. Have a good look through your car pack it may be written on one of your manuals in pen, or contact the previous owners they may still have the code card!
simon, October 2006
