i think u can only get the code direct from vaux. for this you have to go to a vaux dealer, with the original log book (V5) to prove owndership. The dealer would fax Vauxhall requesting the code. YOu usually get the code same day. The dealer would ask you to come again for the code or give it to you over phone. Cost £50 !!!
I had to go through this. Changed battery. had the code for radio/tape. but not for the Cd player. There was no other way I could get it ( the previous owners had mispalced the code...grrrr.)!!!