They're stringing you along. There's no such thing as "an Ofcom report". VM can of its own choice setup a speed monitor on your connection, but that has nothing to do with Ofcom. If in doubt contact Ofcom and ask them how their monitoring of your connection is going.
VM's own equipment shows via their installed SamKnows software that you're below the minimum guaranteed speed, but they're still staling rather than sending out a technician (which suggests it was a completely pointless exercise putting the SamKnows software on the hubs).
Give it a couple of days to see if they come back and get the matter sorted. If by (say) Tuesday there's no progress, then instigate a formal complaint using the online form in My Virgin Media, invoking the minimum speed guarantee, and giving VM 30 days to sort it out, and ask for compensation for the slow speeds and poor support if you feel that appropriate. You could alternatively ask for release from contract without penalty if they don't fix the speeds in 30 days, or to be reverted to your previous contract and speed.
In terms of the minimum speed guarantee, if you need to get formal on the matter, this requires you to demonstrate at least one speed below the guaranteed minimum on three consecutive days. Higher speeds and averages are not relevant, it is the minimum, and the three consecutive days that count. You might want to screenshot and save some of the SamKnows results as evidence.
