Jag, I will try and get a proper wiring diagram with the electrician's help.
Meanwhile . . . . several people have noted that the internal mirror position is not ideal, giving a limited rear view. We have solved this problem by working in two directions, firstly by making a bracket to lower vertically the mirror by 15mm. This involves 'sliding it' down the screen, by making an adaptor.
We chose a 22.5mm transposition / replication of the holes as this equates to a vertical drop of 15mm if one estimates that the screen is a 45 degree slope.
The photos may help understand how it works . . . on the right is an image of the bracket from both sides. It holds 3 spring rods, which attach the mirror to the boss on the screen. On the left is a drawing of what I was trying to achieve.
mirror adaptor plate in 5mm al alloy jpeg.jpg
By using the images one can draw / envisage a bracket: ours came out like this:
mirror bracket.jpg
Here it is fitted, from the inside and outside.
mirror bkt inside.JPG
mirror bkt outside.JPG
The second angle of approach was to raise the rear ride height a bit, by adding another 10mm rubber spacer above the top spring mount [and bump rubber] by using a lower spring pad and cutting off the central 'tube like' section.
We now have very satisfactory rear viewing.
Can someone please explain how to keep the photos in the blog and not end up with wretched links . . . please.