Rover 214 key fob missing, how do I remobilise ignition?

I lost my key and fob/handset. Have spare set (nmo fob though) - can open the car doors with spare key, but without old fob cannot disconnect the immobiliser. Have used the emergency access code with spare key but does not seem to work.
Other possible problem is that at some point, the lock on the driver's side was replaced, so ended up with 2 keys - 1 to open passenger side and 1 to open driver's side (for some reason!)
Spare keys do the same - one opens passenger side, other driver's side (not central locking).
Stopped using the key fob to alarm the car with old keys, as was temperamental about dealarming, so just used keys to open and lock. When locked, the sensors automatically immobilised the ignition anyway. When opened door, ignition would work with the orignal key.
Now with spare keys, doesn't work at all.
What options are there to solve this??