Thanks for the help guys.
Boris - just to clarify my situation- I have 2 spare keys which are the official spares from this particular car... the problem is although they will let me into the car when I try to turn the ignition with these either of two keys I get the immobilser error. Before I lost my other key I never had a problem. My thoughts are that there are problems with the transponders in these 2 keys, but I am unsure if this is something that the dealer will be able to fix - ie is it a physical problem will the placement of the transponder in the key or does it need to be re-coded by the dealer.
You have said that none of the keys work with remote locking, and only key that you had lost work with immobilizer. Since you have lost the key that works with starting the engine/immobilizer, only thing that works now is key blades.
It looks like the guy who sold you the car gave you only one original key, and 2 spares form another car that he probably bought from ebay or similar and only changed the key blades.
So if am I correct "unfortunately you will have to order new key from Alfa and they have to enable it to work on your car (very expensive).
There is no way you can enable key from another Alfa to start the engine, even using Examiner at Alfa dealership.
Remote control can be enabled, but immobilizer NO"
You can try to go to the dealer to try to enable the keys (immob) if they are the original keys from the car, but it does not look this way, there is no reason for them not to work in the first place if they are the original keys.