Intermittent Cranking not starting, odd warning lights.

[soother]

1.0 MPI intermittent no start.

Symptoms: When the ignition is turned on, at first there have been no instrument cluster warning lights at all, and the engine would not crank. then , after a few tries the lights come back, and the engine cranks as normal, but does not fire or start, but some or all warning lights such as ABS stay on during cranking. At the next try the lights may be back to normal, or the same or different lights may be on. It seems random. I think the door buzzer was sounding yesterday too.

This has has happened three times, a month or more apart. The previous two times things returned to normal after maybe 10 mins of trying every so often. Yesterday after much key turning and cranking I gave up and called the AA (2 hr wait, still no start). Mr AA checked the basics, and found no spark during cranking, but he thought there was a spark as the key was released. He also poked the fuses etc, (as I have done myself!) and eventually, maybe by coincidence, the fault cleared again and the car started. Mr AA followed me 10 miles home just in case. The car started ok again today, but I don't want to risk being stranded again.

Vag-com shows the following fault codes

ABS 00668 - Supply Voltage Terminal 30: Signal Outside Specifications/implausible signal
Engine 01314 - Engine Control Module: No Communications Intermittent
Modules 01316 - ABS Control Module: No Signal/Communication
01321 - Control Module for Airbags (J234) No Signal/Communication
16946/P0562/001378 - System Voltage: Too Low (probably cold cranking last winter)
16705/P0321/000801 - Engine Speed Sensor (G28): Implausible Signal. (Note. may be set by excessive cranking)
18058/P1650/005712 - Powertrain Data Bus: Missing Message from Instrument Cluster
18011 - Internal Control Module: Failed Self-Test

Any thoughts? I am trying to work out whether I have a bad ignition switch or other bad power / earth / data connection somewhere.
That last code is worrying, but I think it can also be caused by a loss of power during test. I have cleared the codes and will check again in a while.
Is the "missing message from instrument cluster" error significant?
Bottom line, I don't want to replace the ECU and then find the fault is still there, and have to wait weeks or months to find out.
Thanks.

[JUUL]

I'm not entirely sure but it sounds like a faulty ignition switch. It's really a nightmare to get to, but it might be source of your issues.