Update: (full write up for info only!)
Car just did it to me again. About 50kms from home. Was running fine. Then after about 40kms, a very slight loss of power at first and almost undetectable roughness at 100km/h. (My wife could only tell because of the look on my face!) Gradually worsens and power falls away until I am crawling. As soon as I take my foot off the gas or select Neutral it stalls, dead.
1ST TIME.
Did the fuel purge procedure again. This time listening for fuel 'gurgling' with the fuel cap off. TBH I couldn't hear anything going on at all. And with my head in the engine bay and under the real wheels at back, I'm not sure I could hear a pump at all. I can hear a 'buzz' around the dash which I think I had assumed was the pump, but maybe it never has been (but see earlier electrical test of F10).
After waiting the 3 minutes per purge procedure, engine starts. Very big cloud of white smoke from exhaust. I get going and engine is still running rough and under power. I make it maybe another 5kms before finally quits on me.
2ND TIME.
This time I lift the bonnet. While the fuel pump is purging, I remove the plastic engine cover and 'jiggle' the wiring harness to the injectors etc that we've discussed before. They appear fine. But at this point I'm just jiggling wires!
Engine starts again. More white smoke.
I drive rest of the way back home (45kms) (Without plastic cover in place) with no issues at all.
Except, engine is almost imperceptibly rough at around 98km/h but if you throttle through that to 100km/h you can get it to smooth out until it feels normal again. By the time I got home it was cruising quite happily at 100km/h. In other words, even when cruising fine, there is still a very slight rough patch in the power curve.
To me it 'feels like' maybe 1 cylinder isn't getting all the fuel all the time. Sometimes it is, sometimes it isn't. And I guess sometimes it might not be getting any at all. And at that point the ECU decides to shut the whole shebang down!
Dunno?
