if you look more closely they do the cables with the colour stripe to suit your needs https://www.12voltplanet.co.uk/16-amp-single-core-thin-wall-auto-cable.html and select the colour and length

So they do, and at a good price too.
My bad !

I went ahead and bought a new chassis wiring harness from Sparks.

Nice to just start from a good place, and a I've been making new connectors on my new 13 pin towing socket with shrink wrap colour keys to equate to the Land Rover colour wires

Since I tow a caravan, I do need the ignition powered fridge with it's own earth as well as the purple always powered supply.
Here's a conversion key I made from Landy to standard 13 pin tow socket colours.
which leaves me needing the grey 12V ignition on (battery charge and fridge) in the caravan.
There is a socket on the new wiring harness which I don't know what it is, or if it is powered by ignition. But it is with it's own earth and has red white thicker 2.5mm wire also which may be what I need. Here is a pic of the socket currently not used on a Pick-Up, but possibly for a 110 rear fuel pump, as the harness is the same.

Does anybody know what this connector which is placed in near the middle under the tub, coming from the right to left section of wires and breaking out to the center ?
I will connect the new harness and test if it gets power on ignition. If so it could be ideal for the ignition switched power and avoid the need for a voltage sensing relay installed in an exposed place.

That plug is for a fuel pump

Thank you,
Unfortunately it's connector isn't connected to anything in my bulkhead.
It has a White/red and green/black wire

If I can get the male counterpart connector I could run ignition power to it and attach a name tag, but I don't like modified wiring!
Maybe I should just run a new cable from an ignition live accessory fuse and add it to the loom with the vinyl loom tape I have

Followed by covering all the loom in corrugated conduit

As is done with newer styled looms. Because the vinyl tape gets rubbed off on a Landy and eventually leads to exposed wires, which would be back to my starting point.
Ideally I should use 2.5mm Grey wire which is consistent with tow socket ignition power. Red and white is normally the ignition power dedicated earth!
I've also got some welding to do and a new rear diff oil seal. But I want to have the wiring organised and worked out and it's not the best weather for welding oot!