Okay, thanks, that’s something to look into if I can work out how!
Meanwhile I found this thread: Could not connect to Wi-Fi - #19 by Marky
And went through the steps to try and connect manually using connmanctl, as recommended a few posts down. That got me connected to the network (on the third try but there was maybe some messing around with timing out while I found the password?), but then on starting up Kodi, the wireless network was showing as connected (with IP address, DNS gateway etc.) but with no internet. All the other devices connected to this network think they’ve got internet and the connection here is generally sound so something appeared to have gone astray there.
I captured the system journal, as requested in that other thread: http://paste.osmc.io/izeyugoket
After a reboot, the wifi failed to connect from Kodi in the usual way, and then on returning to connmanctl, I also couldn’t connect manually, in the same way as in that other thread.
The conclusion of that other thread seemed to be ‘try another wifi dongle’, but this one has been known working, on this system, automatically on every boot (I didn’t even have a way to connect via cable in my last place) just on another wifi network. So why can’t it connect to this one?