This worked great, thanks.
In an effort to make it easier to enable/disable the GUI on boot, I put it into a little Bash script, available as a Gist here.
bootgui
#!/bin/bash
# Call with either enable or disable as first parameter
if [[ "$1" == 'enable' || "$1" == 'disable' ]]; then
sudo systemctl set-default multi-user.target --force
sudo systemctl $1 lightdm.service --force
sudo systemctl $1 graphical.target --force
sudo systemctl $1 plymouth.service --force
else
echo Call with either "enable" or "disable" as first parameter.
fi
Afterwards execute chmod +x bootgui to make the script executable.
Call with ./bootgui disable or ./bootgui enable