I was cursing my starter motor and ended up swapping one of my spare rims and tires for another starter only to trace the earth cable between battery and chassi to be at fault.
The earth strap on mine ran uner the battery box against the frame atached to the chassi but took me two hours just to get the damn awkward bolt loose. I then filed and sanded the frame clean and wire buffed the earth strap lug to shine and refitted. Sprayed the patch with Tectol after to hopefully stop any corrosion.
Now she starts like a dream and the instrument gauges are all steady.
Just a reminder to all to keep an eye on your earth points.