Reverse lights not working .

[Sunny43.5]

Isn,t it typical I am in the process of selling our T5.1 and it failed roadworthy as they found the reverse lights werent working , ok that was along with rear brake discs and rotors a bit low . Brakes is an easy fix as I have always done them myselves , but the reverse lights have me stumped . After a bit of research it seems a fuse no 15 is for those lights but mysteriously I cannot even find any fuse in any 15 position in any of the fuse boxes , I have tested every single fuse even the ones under the seat and engine bay but none are blown . I now suspect it could be a reverse light switch built into the DSG or maybe Im wrong , now what is strange when reverse is selected the reverse camera and head untit switch to those cameras so something is working . So question does anyone know if there is a switch and where is it located .

[Rebuild]

didnt you replace the rear lights with non VW LED ones a while back? All reverse leds working? If LED, did reverse lights work when first installed?
Try your old lights?

remove a rear light and check for volts?
Im guessing there is a switch at the gear selector. Maybe it senses your camera, but not quite enough to sense reverse. Worn switch? Probably not this, i mean, switches either work or they dont, right!

any relevant fault codes?