Decided to make a start on the brake pipes. The rear fix as they seemed the least complex. Attached the 4 way splitter with a bolt rather than the rivnut. The hole in the chassis is too big for the rivnut. They connected the brake light switch to the splitter.
I started by bending the brake pipes without connecting to the splitter or the flexible braid which I had temporarily fixed to the chassis. This gave me the freedom to bend the pipes in my hands away from the chassis. But, when I came to screw the connectors into the splitter and flexible hose it changed the pipe length once the nuts were tightened. So second attempt was to anchor one end of the pipe (screwed into the splitter) and bend the pipe whilst attached. Much harder, but eventually allowed me to reach the braider connector via a suitable anchor point for a P clip. Courtesy of the local B&Q shop I also added some clear plastic pipe to avoid chaffing as the pipe bent around the chassis at each side.
One thing I couldn’t figure out was which braided hoses went on the front and which on the rear (small or large). Without the suspension and brakes attached it was 50:50. I must remember to ask.