Hi Painter ,
It's in part 6 of the driver's handbook:
Inertia switch
In the event of an accident, an inertia switch may trip, isolating
ignition controlled circuits, including fuel pump operation.
Simultaneously, the doors will automatically unlock. Once the
switch has tripped it must be reset before attempting to restart
the engine.
Note: The doors will
not unlock if the inertia switch is tripped
when the ignition switch is in position ‘0’.
The inertia switch is located behind the trim on the left-hand
side of the vehicle, forward of the door post below the fascia.
The reset button is parallel with the trim panel top edge.
Resetting the switch
WARNING

:
To avoid the possibility of fire or personal injury, do not
reset the inertia switch if you see or smell fuel.
If no fuel leak is apparent, reset the inertia switch as follows:
1. Turn the ignition switch to position ‘0’.
2. Press down the rubber reset button on the top of the inertia
switch.
3. Turn the ignition switch to position ‘II’, pause for a few
seconds, then return the key to position ‘0’.
Edit
As to how you get to this when the passenger door won't unlock and the window is up ,
perhaps this may work
open the bonnet , there is a power pick up point on the passenger side of the engine bay protected by a black rubber cover , you could try connecting the positive side of a slave battery to this and the negative side to a good earth point using good jump leads , this may provide power to the ignition and door locks to at least open the door ????? Worth a try ?????
Hope this helps ,
Nik