Why not type the external number in the detination of the incoming call route?
E.G
Incoming number = 4543331
Detination = 00441214555789
This will redirect any incoming caller who dials 4543331 to the International number listed.
This is the same for any extenal number, Local,National,Mobile etc..
setting up fictive users then diverting whastes system resources that could be used elswhere.