That engineer visit will be a total waste of time. Your levels are all a-ok.
Even if he agrees its over utilization he will not be in a position to do much about it.
I had many of mine agreeing thats the problem, they made various phone calls to "head end".
Nothing ever happened until virgin were just so sick of hearing from me they increased capacity in the area.
This gave me 6 months of a solid connection. As you can see from my bqm its all started going wrong again.
They simply do not care about anything but the minimum download speed that they guarantee.
All they could do (but wont) is set up a automated sam knows test.
This would run a sam knows speed test every hour to your router.
IF your speed are not up to snuff they MAY do something about it.