Hairychested, according to books you should be happy to know that a key is available for the 406, it wont have the buttons for central locking as that is dealer only so you would have to actually put in the door to open, but immobiliser is fitted and programmable. We’d charge £25.
Sofaking yours is also available IIRC will have same functions as Hairy’s key and same costing.
Your local key cutters should be able to do these if they have a transponder machine.