I've teased the wiring out a bit, so that it's easier to see what's going on....
There's a 3-core cable coming from the rest of the house, which then is connected to a 3-phase, 4-core cable inside the switch base-unit before heading outside....
The brown goes into the power-switch and the brown that goes outside comes out of that switch.
The blue from inside is connected to the (blue-sleeved) grey via a connecting block.
The black from outside (brown sleeved) is just floating around in the air, and not connected to anything!
This suggests 2 things to me...
1. The grey must be the neutral, and the brown the live.
2. Why on earth bother with the 3-phase cable, when the 3rd (black) wire isn't connected to anything!!
Weird!
Rgds... Ray