Finally found some time to have a go at hunting for the fabled front auxiliary light wiring.
https://youtu.be/bjCdP_tTLc8Not the most stimulating video you'll ever watch, but I felt this was the best way to demonstrate what I found, or rather didn't find

Unless anyone has any further ideas, I think the solution here is to build my own fused sub loom with relay and forget trying to trace wires that don't appear to be present.