1997 Primera P11; power locks nonfunctional

Hi. The power locks have suddenly stopped working on my UK 1997 Primera P11. The car responds to the remote keyfob with flashing of indicators only, and fails to unlock any other door when unlocking the driver's door with the key. In addition, since the system failed when the doors were locked, the deadlocks prevent passenger and rear doors from being unlocked from the inside.
I have since noted that the rear window defogger/ heated wing mirrors have also ceased functioning, suggesting an electrical fault around the "Smart Entrance" unit. I have checked every fuse in the driver's side under-dash panel, and the engine bay panel, and they are all good.
I have also replaced the "Smart Entrance" unit, and experiencing similar symptoms (albeit with no response when using the remotes, as I suspect remote codes are stored in the "Smart Entrance" unit itself).
One thing I have been unable to check is the circuit breaker mentioned in the wiring diagrams in my Haynes manual - does anybody know where this is?
Has anybody got any ideas what I should check next?

Thanks in advance for any advice you can provide.
- PhoenixGB