Thanks for replying. I realise it’s the holiday period, I’m not expecting immediate responses 
Following your instructions in the link I’m lacking the eventlircd. Should I install from here or is there a PPA? osmc/package/eventlircd-osmc at master · osmc/osmc · GitHub
I don’t know if this would throw a spanner in the works for understanding where the problem is - I discovered that the Play/Pause button works as you’d expect in Spotify, as well as elementary OS’ bundled music player (labelled Music but I think it’s called noise to the system). None of the other buttons seem to do anything (not that they necessarily would do much), though it doesn’t seem to indicate the issue is with how Kodi is reading information being sent to it on Ubuntu-derived installs, rather than it being an issue in the OS?
Based on your advice in this post OSMC remote mapping on KodiBuntu - #16 by sam_nazarko - running kodi with the command ./kodi.bin --lircdev /var/run/lirc/lircd - would that mean always starting Kodi from terminal instead of the dock icon? If that’s so I may cut my losses and make do with it as it is.