Z-Wave integration - stumped by failure

I’ve been considering that but the official advice seems to steer quite firmly away from that.
Nothing to lose I suppose other than hours of my free time.

Okay, so the direct install only took about 15 minutes, but it doesn’t work! There were loads of errors when you run hass and I’ve no idea about most of them. For sure the last one must matter as I can’t reach the Hass via a browser. It says:
Failed to create HTTP server at port 8123: [Errno 98] error while attempting to bind on address (‘0.0.0.0’, 8123): address already in use
Even after a full reboot netstat says 2123/python3 is listening.

That implies that another instance of HA is already running. Are you running HAOS on bare metal or under Virtual Box.
If you do a search on the error message, you will find several posts here that might be relevant.

Done the search so I know I’m not alone with this. The answers were technobabble for a man of my limited knowledge. Given up on VirtualBox, this was bare metal.

That sounds like an IP address conflict. Are you sure you don’t have another instance of HAOS running on the network?
After it’s booted, do you even have basic network connectivity? Can you ping other devices on your network and does your device get assigned an IP address?
What hardware are you running HAOS on?

Well I could web in fine when running the VirtualBox installation, so I’m confident my basic networking is working (plus I can browse the internet). As for a second instance, I’ve no idea where that would be or how to check for it.
Machine is Celeron powered, host OS is Mint 19.

How can the host OS be Mint if you have installed HAOS onto the PC? If it was a bare metal install, then HAOS will be the operating system you are booting off.
To eliminate virtualisation as I suggested and boot directly into HAOS, you need to follow the installation instructions here: https://www.home-assistant.io/installation/generic-x86-64

Sorry, misunderstood what you meant by bare metal, thought you meant no VM or Docker. A dedicated machine is not an option for me (unless it’s a Pi which I can’t currently buy).

As it’s not related to Z-Wave I’ve started a new thread on my installation problems at Install Home Assistant Core failure when running hass