Door lock problem.

[Flash635]

I just bought a 1997 Mondeo LX wagon and I'm having a bit of trouble with the door locks.

I can lock all 3 doors with the key but I can't unlock them. The key works in the ignition but I have to withdraw the key about 1mm for it to turn.
If the key bottoms in the ignition barrel it won't turn.

From what I know of Fords you can lock the car using any key that will go in the hole but not unlock it, is this the same if the key is worn?
But then it wouldn't work in the ignition would it?

Maybe some previous owner has changed the ign barrel and left the door locks as is?

How can you tell if you have a remote central locking system?