Hi, from our server side networking seems good but there may be issues due to international routing.

You may want to try changing the download URL from cdn.openmamba.org to hetzner3.openmambaorg, e.g. the current livecd URL would be:
http://hetzner3.openmamba.org/pub/openmamba/media/devel/livecd/en/openmamba-livecd-en-snapshot-20210828.x86_64.iso

The default download is from Italy, the alternative URL is from Germany, so there might be differences in download speed from your location.

Thanks for the suggestion but it made no difference.

I did find a torrent for ‘openmamba-diskimg-livecd-en-snapshot-20210630.x86_64.img’ which I installed but there were 367 updates and after that despite several attempts it would not reboot to a desktop, giving different errors each time.

I'm sorry it didn't work.
When I can get the necessary information I always try to find a solution.
The distribution is undergoing the migration to the flat /usr filesystem in rolling updates modes and the issue here (specially when using a former livecd version) could be that a /lib/systemd symlink is missing, this in short can be fixed by logging into a console (CTRL-ALT-F2) and entering the command:
sudo ln -s ../usr/lib/systemd /lib/systemd.

I guess in any case I might have more luck with the most recently published image. I'll leave the link for this open on a spare machine for the required number of hours and just hope the file is intact once it gets here.

Out of interest the only two programs I can't live without for work are Google Chrome and the Slack desktop. Hopefully both these can be installed on openmamba?