Reverse light help

Hi all and a happy new year, I'm having trouble getting my reverse lights working on my 54 octavia vrs I've changed the switch checked wires well from what I can see near the switch checked all fuses in the main fuse box and checked the bulbs and still no luck I don't have a wiring diagram and have not bought the Haynes as I've heard it's not all the great.

So I was wondering as some ideas of what to check next is there a relay under the dash or is the control unit under that dash part of a controller for the reverse lights??

Or am I better off running a new cable from the switch to the lights I can't remember I it was a negative switch if so there must be a relay somewhere I have diagram an service manuals but nothin to say much about the reversing side of things I don't have reversing sensors either

Thanks guys