I hung the wiring harness on the garage wall laid out as in the car, then starting at the fuse box identified each circuit and removed them. Check, check - cut!
Having it bundled up in separate pieces is no good as you will keep going over and over the same bits.
What I was left with was an overlong basic loom that I could lay on the chassis and route effectively.
I know the wiring diagrams are confusing as they are individual I found it quite easy having it laid out and learned a lot along the way about the circuits and how they work.
Steve