Thanks for the advice.
So I repaired using the guides published. As suggested not too difficult, just very fiddly.
Top tips from me.
Use black cable for the earths, it saves a bit of time when checking and Feels more correct.Not sure if it makes a difference but tried to work out the correct path way for the black wires, not just join black to black.
Don’t wrap your wires until you have given it a good run and got heat in the engine bay. Allows for easier checking and weak joint checking.
Use a powerful enough soldering iron and a strong flux especially for the existing wiring ( I used a plumbers flux
Play some floyd and chill.