Although not too different from the picture at the start of the day, this is the end result of nearly 6 hours of fiddling.

It would have been a bit quicker if:

1. I had checked that all the fuses were in the fusebox! Lesson learnt and a real "Doh" moment.
2. I had remembered how I'd simplified the brake fail circuit from the original idea. I had to open up the small case just to see how I'd modified it

The dipped beam works too, in fact everything works as it is supposed to and I managed to keep all the smoke in the wires, so I'm quite happy about that :-)