GRUF--
Painless wiring is made out of modern components and modern high-temp
oil resistant wire.
Sure they do some leaps in logic in some of their diagrams, but their stuff WORKS from a harness standpoint, and is a durable industrial item.( their EFI harnesses are a mixed bag, but their chassis - relay fuse block stuff is ROCK SOLID) I have installed about 20 of their cirkuit boss blocks in various cars, a bunch of their 65-66 mustang harnesses and their generic chassis harnesses.
I also am a fain of the Lucas stuff ,-- the lucas repro stuff now is better than lucas used to be but nowhere near the durability of a motorcraft, packard electric,delco (painless) or JT&T item.
I think you can put some lucas items in place to make it look quasi British and correct whilst still having the thing actually work.
Remember: do not accept a lucas part in anything other than the green and white lucas box. or on a green and white lucas card -- there is some serious junk out there posing as original L'.
I have thought about trying to get some of that cloth covering and having hi-temp wire inside it to make it look that part, but be reliable.
Gruff-- have you thought about what you would want to do for headlights and an Alternator >? what about an ignition system >?
--Steve