Just thought I'd post an update on this. My power sockets went out again today when I went for lunch. They were showing low voltage again.
I bought a probe on the way home and tested the kick panel. It's definitely a loose wire/contact at the panel. There are a couple of wire looms that disappear near the kick panel so I couldn't determine which one was the culprit. I did "fix" the problem by kicking the panel a few times
. Power came back up to full after that.
I need to pull the plastic paneling in the footwell to have more direct access to test the wire looms. That should also let me unscrew the fuse panel to see the back of it. Just what I wanted to spend my Saturday doing