Does anyone have a schematic for wiring up a switch in the trunk(boot) for opening doors. This the second time I couldn't unlock door with key or remote. The battery was down and the door handle lock malfunctioned.

 

I think your approach to the problem is a little misguided. First the door and boot key lock is mechanical and do not rely on battery voltage. Only the FOB and dash button rely on the lock solenoids. First I would open the drivers door and drench the lock mechanism in WD-40 and then spray the interior of the key hole. Once that is done close the door, lock it with the key, then unlock with key and open the door. Repeat a half dozen times to exercise the mechanism. Do the same with the boot lock key hole.
If you use the key to open and lock occasionally it want freeze up again and thus no need for a switch.
If you are set on a switch go to JagRepair.com - Jaguar Repair Information Resource and you can download the complete electrical manual.