Thanks again.
The problem is the wrong key was used to start the car and the ignition is locked in the "on/run" postion, and the key cannot be removed or turned.
I know I can just leave it in there, and use a universal starter instead, but I would prefer not to.
I have a strong suspicion that there is a spring/clip/pin that must be pushed and the whole barrel will simply slide out (i had to do this on another vehicle previously-and had to drill a very small hole to push the pin down).
The cylinder has some movement in the assembly (like being held by a clip/spring), so this further suggests to me that it can be removed with the right technique.
Thanks again