Yeah, it wasn't until we had it all put back together that we noticed that the spindle was the wrong length, so we're fully expecting it to happen again. I think it's a problem that there's nothing stopping the drive-side cup from going into the bracket if it starts to move along with the crank -- we're going to look for one with a lip/rim to prevent that next time. I'll get my greasy fingers on a camera for photos and show you what it looks like next time I'm in the shop.
At least now I know what it's supposed to look like and will be able to tell if it starts moving around again. You know, BEFORE the pedals are full-stop. And if/when it happens again, we've got a couple of strategies (and a different guy at the shop who is the go-to guy for English bikes) to fix it.
I've also got a fun gear-slippage problem, but that's a project for next week too.