stupid.

[kevtherev]

After a succession of warning light failures, oil light flashing, buzzer randomly sounding, temp gauge flashing, reading high.
I took off the binnacle and took a look, light bulb moment and remembered the 14 pin connector, felt down for it, found it and pushed it fully back into its socket.
All lights and gauges returned to normal
It is easy to be mislead by electrickery.

I have only one high beam bodge to remove.
The oil pressure gauge was extremely calming when the buzzer and light went off at 75 in the outside lane

The cause, and I remember it now, was bone jarring pothole that must have shook the connector loose, and started the random light failures as it worked its way even looser.

[marlinowner]

The PCB is made with shorter tracks for the +12v and ground pins in the 14way, so if the plug is slightly off you can easily lose the ground and things half work - I had the coolant light coming on if temperature was just slightly high.

[kevtherev]

Which is exactly what happened.
I think my lesson was learned, it was the gradual loss of functions which threw me, so a logical thought for the 14 way did not occur.
The connector was at an angle half in one side fully in the other.
Each van jarring clunk knocked out something else along the line, that was the common denominator that bought on the light bulb moment

[Aidan]

the 14 pin plug should be retained by a shrouding plastic around the foil edge that is often missing
part number 690 919 060, VW describe it as binder
Mick will have them

[kevtherev]

Thanks pal
I'll get in touch with him