More modern car stereos are usually coded with a VIN rather than an old style 4 digit PIN.

If you'd put another Corsa stereo in yours you might get nothing, or an annoying beep every few seconds.

CD technology is pretty old now. A quick and cheap instant solution would be one of those FM transmitters that plug into the cigarette socket. Connect it to your phone or MP3 player then tune the radio into the frequency of the transmitter.