Firstly, thanks all for the advice I found here, for me a slight variation worked
nvidia-installer -n reboot pacman -R -u nvidia-utils pacman -S nvidia-390xx
Had to remove nvidia-utils otherwise installing nvidia-390xx failed to install, cause of existing files.
Also just cause I’m suspicious, I subsequently uninstalled noveau.
I’m a newbie to Antergos, so apologies if this is a naive question.
Do I need to do anything to ensure that future upgrades do not install newer versions of the nvidia drivers?