Igor - firstly thank you for taking the time to reply.
Running the command does show that SSH is correctly listening on my port
sshd 23650 root 3u IPv4 7376014 0t0 TCP *:XXX (LISTEN)
sshd 23650 root 4u IPv6 7376016 0t0 TCP *:XXX (LISTEN)
The firewall settings are ok...
I am running a new VPS server from Heart Internet running Ubuntu 14.04.5 LTS and Plesk Onyx 17.0.17. I have enabled the Firewall extension and have modified the ssh port to use something non-standard. This port is allowed through the firewall, and after applying the rules, I have been able to...