An update, in case anyone else encounters similar issues.
Firstly, Virgin finally confirmed there was an update but it took many calls and many very unhelpful people to get there.
As mentioned before, I took my equipment to a friends house and confirmed it was working, additionally my company sent me a second teradici box to confirm this and indeed it suffered from the same issues. Bringing this to Virgin I got absurdly unhelpful response ranging to "we don't support that VPN" (it's not a vpn) to "there's nothing wrong and therefore you have to talk to your company, it must be their end".
I did finally get one very helpful operator who took my request for a new superhub at face value with the evidence I presented with no questions asked. That was very helpful, although I had to wait until Tuesday for this.
In the meantime the guys in the office ran tests with me using Iperf3 and we established that the problem was with UDP traffic not getting through at all - given that the teradici uses UDP this seemed like the cause. Again, nothing helpful from Virgin at all on this, in fact it was more or less complete denial of the problem.
When the new superhub 3 turned up I installed it and was immediately back up and running, teradici connected.
From this I can only speculate that there was a problem with the update as originally thought - why else would the superhub stop working with the Teradici traffic overnight? Bit of a mystery but certainly something that should be investigated.
For anyone that may encounter similar issues I found these threads helpful (regarding UDP problems)
https://community.virginmedia.com/t5/Speed/UDP-issues-on-SuperHub3-collective-thread/td-p/4382720
https://community.virginmedia.com/t5/Speed/My-350Mb-connection-is-throttled-to-10Mb/td-p/3953746/pag...
I'm glad that simply replacing the superhub fixed the problem but I have to make a number of complaints:
1.) Trying to get a replacement hub sent out to me was like trying to draw blood from stone, despite me presently various evidences of a problem, which leads to the next point;
2.) Very poor troubleshooting and almost complete dismissal of my points, with a recurring suggestion that it must be my equipment, even after I had tested at another property served by Virgin on the same street, with no issue. How many times must I reboot the hub?
3.) Complete ignorance of the UDP problems (as per the above threads) - when we had narrowed this down with the iperf3 tests, the call operators just didn't know what to do with it and the only commentary was that because watching youtube and web browsing was fine, the connection had no issues whatsoever.
This cost me several days of downtime, during which several operators promised callbacks from supervisors that never materialised. Completely unacceptable in the current situation.
