@adhsmith Yup my hub does indeed show a 3.1 channel but most are 3.0.
That's how DOCSIS 3.1 works under VM's implementation. There's 31 downstream D3.0 channels, and one downstream D3.1 channel. All channels work together to share the load, and at maximum bandwidth on a 1 Gig connection something around half the bandwidth comes through the D3.0 channels, and the other half comes through that single D3.1 channel.
If that sounds a tad odd, it is because DOCSIS came about as a way of offering data transmission crammed into a few bits of spare RF spectrum on analogue cable TV networks designed around downstream traffic, and so from the very start data was an afterthought. Since then it has been incrementally improved, but each increment is built on a wobbly foundation, and everything has to be backwards compatible with older versions and older equipment. What's being achieved now is incredible, but DOCSIS is a bit like the last days of CRT monitors and TVs - the outcome of the technology is superbly refined and capable of great things, but it is still a sunset technology that on close inspection is Grade 1A Heath Robinson, and some of the underlying problems (in particular the RF analogue local loop) will be exceptionally difficult to resolve. The best effort scheduling that @Eeeps mentions might be addressed under the Low Latency DOCSIS arrangements provided for (but not mandated) in DOCSIS 4.0, but that would require new hubs that don't yet exist, and a full network upgrade which wouldn't even be started until 2026 because the D3.1 investments will have to be written down before VM go for another upgrade investment binge. Even then, how well LLD works in practice remains to be seen - it isn't genuine low latency, but rather packet prioritisation. If the majority of uses by then are latency sensitive, LLD is unlikely to be effective.
If you're noticing 10ms differences, then you'll have to hope that you don't get a bad day, because this is a good day on my VM (Hub 3) connection:

And this is a bad day:

I bet you're thinking "I wish I'd known this before committing for 18 months" !