Yay! I've now passed the rite of passage o be a proper beekeeper and hurt my back!
Seriously though, I was moving a full super and I must have lifted and twisted my back, and pulled a muscle or something.
In any case, the split hive is growing nicely. It has now completely filled the brood box (with bees) even if it appears that the queen isn't laying much. Pattern is nice though. I haven't been through all the frames, so there might be more brood than I've seen. The colony seems healthy, there is brood and they're nice and docile. That's good enough for me, they'll be left alone for a few weeks, until I need to check on them for winter preparations.
The other colony is nice and strong, but it seems to be foraging enough to feed itself and possibly a little more to put away, there isn't much of a flow, even with the recent couple of rainy days. Not entirely unexpected, and I'm happy enough they're not going through the stores. The flow will start again around September.
Looks like I will need to get that extractor I was eyeing...