Probably a loose or maybe corroded connector. If it's intermittent like that it's almost certainly something fairly simple and mechanical to blame.They came back! I don't get it.
It was working on the first half of a journey. At some point - including one full switch off and restart lasting about 1min - they stopped.
I then got home, car wasn't used for about 4 hours but they were working when I got back in.
The window was working (dropped when I opened the door), the mirror auto-dimming was working, the door lights were working. However none of the controls worked and there was no lights on the controls themselves.