Post Xmas holidays I have finally had time and the courage today to perform a factory reset on my Vodafone THG3000 Hub as suggested by VF support before Xmas in an effort to get my UL speed up to the contract spec of 105 Mbps..
First tried the "
factory reset" option within the GUI, this doesn't work, just performed a re-boot, all custom setting retained.
Performed a factory reset via the recessed push button at the rear of the Hub, this worked.
After restoring some basic settings, re-established an internet connection to run a speed test.
Contrary to expectations and very much to my surprise, UL speed was now up to spec @ 105 Mbps

Another bonus, the Vodafone Android app which had stopped working was now able to establish a Wi-Fi connection to my mobile again so enabling my old Wi-Fi 9 character PW to be re-applied, the Hub GUI will only accept a min. 12 character Wi-Fi PW, saved a lot of trouble resetting all my Wi-Fi devices, Google & Shelly devices can be quite time consuming to re-configure.
Took some time to re-enter my network MAC/IP address reservations, the Hub interface can be very slow to update.
Was tempted to try a configuration restore which I had saved just prior to the factory reset, decided against just in case it upset the updated settings which the Hub must have downloaded during/after the factory reset.
Noted that the Firmware and Bootloader revisions have remained the same, can only assume that the factory reset and re-connection process has removed the UL 30 Mbps clamp that the support agent said was active on the router?
Happy with the overall result and have cleared up the TOBi non-connection issue along the way which hopefully won't be needed any time soon

Perhaps VF support in this instance anyway is not as bad as it's reputation

Edit: Typo correction.