Right the next steps.
First, because today was warm and wet, when I opened the garage door I got a light covering of condensation. This allowed me to test the heated screen, which was pretty good as it turned out.
They do tend to have odd non-working strips..............

Back to the story then.
The next image shows my supplementary earth lead from the battery carrier to the chassis. Not really necessary but a belt and braces add on. It tucks away quite nicely.

At the rear I removed the earth connection pictured here, scraped away some of the coating under the fastener (to improve the contact area), and replaced it with a dash of ACF50.
I found a cigarette stub inside the spare wheel cavity.....burned right down to the filter tip.

Then I made up a supplementary piece of earth cable for the bulkhead area.

Behind the brake servo are two earth connections onto the bulkhead just visible here. I piggy backed my new extension onto both.........The one on the left put up a fight, it was hard to start the nut, and access is terrible............

This is a better shot if the one nearest the gearbox:

The end of this cable is attached to the fastener here.....this bolt goes through the chassis above and to the left of the clutch pedal in the drivers side footwell. Again dripped with ACF50, then Tectyl 506 wax over the top.

My thinking is this........the immobiliser issue seems to be with cars from 2016, and of course what changed in 2016?.......... the chassis treatment. So then I'm wondering if the earth connections through the autophoretic coating might not be as robust as through the galvanised finish............... and might degrade over time.
So we'll see what happens now.
Finally I have one more question for the panel..............Now, my immobiliser light flashes regularly without the key in place.
With the key in place the light goes out in two seconds and stays out, even when the engine isn't started.
If I leave the key in the ignition, the light stays out.
BUT....I have this memory that when my Plus 4 was new, with the key in place but the engine not running, it flashed rhythmically, like two flash, pause, two flash, pause, and so on.
Can the panel check this out please and report back?
Thankyou!
