The chances are that your original radio is a Vauxhall baged Blaupunkt, Philips or Delco with a standard ISO Connection at the rear.
It will depend on what "Make" you fancy buying and the reason for changing the original.
If it`s only because the original is faulty, then buy one of the above names from Ebay (preferably taken from a Vauxhall ) then it should be a straight swop.
Make sure you know the MAKE+MODEL of your original and also the SECURITY CODE.
Useful advice can be obtained from this website
www.tinyurl.com/4ydhop
RegWorts
September 2008