I have a vauxhall and since a battery change the radio has been dead as it needs a code. I have been told that if I get the serial numbers of the set it is possible to get the code, can anyone help?

I have a type car 300(f) and here is the details off the radio that I could find:

24 455 376
7 640 852 520
GM030M23053956

Many thanks, Martin.

Martin, January 2009