anyone scratch built a harness

[Ianr]

I am adapting a stock MX5 Mk 2 loom at the moment and wish I had been able to make my own, I am sure it would be simpler - but - I am using the standard ECU which also has an immobiliser ECU and transponder key set up. I have not been able to find a complete UK wiring diagram but have got a selection of Miata ones which are different in a number of places. If I were to use an aftermarket ECU I am sure it would be relatively simple to make a loom up but not really if you want to keep costs down by using the old ECU's