Wow, that's spooky - just answered an almost identical question on DigitalSpy. Look here;
http://www.digitalspy.co.uk/forums/showthread. php?t=1049590
There are a number of sources for the radio code - you can try the original dealer (look in service book) or get someone to decipher the code from the radio's serial number (using a special computer programme). You will find links to the various Vauxhall owners/drivers clubs forums in my answer above - they can help with the latter.