Thanks to everyone on Facebook who helped with my lights issue. Special thanks to Paul Volker who pointed out that blue is positive not negative. A positive common – who knew? The decoder instructions were certainly silent.
I realised I had painted my reversing light red so quickly added another light and, amazing, they worked! It took another 10 minutes to program them so that they came on in the right direction with all of them on in reverse.
I feel happy!
The reversing light still needs painting and glueing in place so there’s a big of slack in the wire.