If, like me, you cannot remove the barrel because the wheel lock was on then your only other option (short of removing half the steering column), is to do what I did. Drill out the inner barrel with a metal drill bit. This could take an hour or two depending on your drill but eventually it releases the wheel lock and allows you to remove the ignition barrel completely. You can then replace the barrel (I got one from a breakers yard for £30).
James North, August 2008