How do you change ignition barrel on 2002 vauxhall zafira?

To remove the ignition barrel you need to be able to turn the key to position II. On the barrel casing you are looking for a small hole in to which you insert something like an Allen Key. The barrel can then be extracted. If you can't turn to the second position then its time to get the drill out and carefully drill the contents of the barrel. It's worth tapping the casing with a hammer whilst turning the key if the barrel has stuck before drilling.