The part number that you've given seems to be what they now use for the psot-war B&M models..It looks from the diagram as if they have incorporated dip switch, instrument lighting and brake lamp into the main harness. This is not how it was done on the pre-war and wartime machines, and several of those functions were not present on WD models at different periods.
What is it exactly that you're intending to achieve ? If it is a visually correct 1940 loom then the ready-made item is not a good starting point. All wires (except dip switch on early 1940 models) were black with coloured rings to identify.
from what I have noted is with modern replacement harnesses - the horn wiring is directed to the front of the engine on the bike as opposed to the earlier bijes which had the horn mounted under the seat