I've used Vehicle Wiring Products for most of the cable, connectors and tools when I re-wired the P5B.

"We can supply all the parts you need for vehicle wiring. Our stocks include thousands of cables, terminals, connectors, crimp tools, switches, fuse boxes, brake pipe and fittings etc. If you are repairing or carrying out modifications to your vehicles’s wiring or manufacturing a complete harness you will find the parts you need in our comprehensive on-line catalogue. 

Materials stocked for classic cars and motorcycles, modern vehicles, motor sports, kit cars, campervans, caravans, marine craft and narrowboats etc. We have been supplying vehicle wiring parts worldwide by mail order for over 25 years."

www.vehiclewiringproducts.co.uk