The van has factory fitted towhook, rear camera and rear sensors.
I've removed both rear light cluster panels.
1. Nearside there is an unused two pin plug with thick red/black and black wires
2. Offside a matching plug with brown/white and black wires.
3. Additional in the offside there is a three way plug fed with two thinner wires white and black.
I think #3 is provision for a 12v auxiliary socket?
Any suggestions please.
Regards Nick.

#1 #2 heated rear windows if fitted maybe? ... only guessing.