Found it.
For anyone else on a similar learning curve, here is what I did.
I read benhex's newbie guide.
Then, I read benhex's newbie guide - again
I set (Key VPN_PROV to Custom and installed the docker, started the GUI and got an error - invalid IP.
I googled and found that you can download OpenVPN Configuration Files | NordVPN such as xx99.Nordvpn.com.tcp999.ovpn and/or xx99.Nordvpn.com.udp999.ovpn (files) which I copied into \appdata\delugevpn-flexget\openvpn folder on my server.
I noted the VPN_PROTOCOL (Key 6) was set to udp, so I used Notepad++ to open the xx99.Nordvpn.com.udp999.ovpn and found an entry for 'remote', which consisted of a IP address 999.999.99.9 which I copied across into VPN_REMOTE (Key 4) and a 4 digit (port) number which I copied across into VPN_PORT (Key 5).
I then used the remaining defaults and apply'd the changes, stopped and restarted the docker and ran the WEBUI, which ran and asked for a password.
Since I am in, and have downloaded a ubunto iso (been following Spaceinvaders videos ), I think I have it working correctly, ie i'm downloading via NordVPN (2.3mb rate)
Many thanks benhex
mark
"always nice when your on a steep learning curve if someone passes you a ladder"..