Clues in the name really innit?
Virtual PRIVATE Network
Short of DPI, how would VM be able to tell you are using a VPN for work for a specific subset of clients (councils in your case) or indeed for a larger subset (say corporate VPN's) of users? Why would they care? VPN' use fairly little data compared to say streaming Netflix. The reason there are clauses limiting working from home in the TOS is to prevent claims for liability, either through service faults or technical support.
How many resources would it take to monitor every VM connection in the UK for suspected corporate VPN use and kill the connection after an hour? The answer is "more than it would free up just ignoring it"
So I have to echo the above- sounds like lazy tech support employer end to me....
However we should not jump to conclusions. How does the connection perform when NOT connected to a VPN? Have you tested it connecting to a different VPN?
Next
So we can help us to help you, can you
Go to your Superhub Log in screen
Do NOT log in.
Little button top right.....

Can you post Upstream, Downstream and Network logs.

Screen caps are nice, C&P will do- Don't stress about formatting if you C&P. Someone will get a look and see if there's anything obvious amiss.