Seems my reply to this got lost…
Got this working! Removed the .nvm directory, removed the symlinks, shutdown pm2 and re-ran the installation script and it all went in fine!
sudo rm -rf ~/.nvm sudo rm -f /usr/local/bin/node sudo rm -f /usr/local/bin/nvm pm2 stop mm sudo rm -rf ~/MagicMirror bash -c "$(curl -sL https://raw.githubusercontent.com/MichMich/MagicMirror/master/installers/raspberry.sh)"
I got an error on npm not being the right version, so upgraded that:
sudo npm i -g npm
(Note sudo is working now, which it wasn’t before) And now my node and npm versions look good and pm2 is running MagicMirror again!
pi@raspberrypi:/ $ node -v v9.11.2 pi@raspberrypi:/ $ npm -v 6.5.0
Thanks everyone for the help!