Now for the instalation of the battery tester. Well heres the circuit after being sprayed with plastidip:

so ive decided the place to put this is on the fuse box lid, seems quite relevant, so off it comes, and with the digital calipers i measured where i wanted to mount the switch and LEDs, on the same line which can be scored with the point on the calipers, but just a light score so damage doesnt occur on the calipers:

The switch needs a 12mm hole, but i started with a 5mm bit:

then did it again with a 12mm bit:

trim the edges of the drilled hole, to allow the switch to fit flush, put it in and tighten the nut at the back:

now measure the places for the leds, i left 10mm between each one:
i drilled the holes out to 5mm, its big enough for the leds but ill be using proper led holders when they arrive which may mean 7mm holes. anyhow the leds look like this:

Then to mount the circuit i decided just on the lid of the fusebox itself, so on with a blob of sticky glue:

press the circuit down:

then tidy up the wires as well, ive clamped them down onto the underside of the fuse box with cable tie points:

this means that the battery tester will have a neat plug on the end of it. A +ve and -ve from the battery. Which is available within the fusebox, supplying the LED lights for under the bonnet.
But for now i have a fusebox lid which looks like this on one side:

and this on the other while the glue sets:
