Ah, ok. tbh, I'm not sure what an "off-net" address is or what implication it has. I've figured how to do a traceroute. Am I ok to post the results here - I'm not sure what they mean. Apologies for shamefully naive response

You can Private Message me with the results of your traceroute if you want. I'm certain its a firewall issue as the provider we have tends to drop packets from big ranges of the world due to cyber attacks. I can submit a ticket!
-dvd