Finally got my Nextbase front and rear cams installed yesterday by a local autoelectrician, they hardwired the cams through a spare fuse in the fusebox.
Asked them to photograph the fusebox which they did and I am waiting for them to email the pics, will post it when they arrive.
While talking to them they said that all wiring must not crossover any airbags. This is especially true for the power cable, if it crosses over the A pillar airbag when the airbags deploy the force will rip the front cam off the windscreen and is liable to cause serious injury.