Well there's nothing wrong with your downstream power levels or the signal to noise ratio, both are well within spec.
As to the RS errors ... pre RS errors are to be expected and are not an issue but post RS errors should not be occurring except when the hub auto-renews DHCP. Try resetting the post RS error count and see whether any more appear.
Can you also post your upstream data and we'll see if there's anything amiss there that might be causing your disconnects.
Yes that's what I was after. I can see immediately that your upstream power levels are too high and this could be the cause of your disconnects. The acceptable range is 31 to 51 dBmV but both your upstream channels are at 52. You really need an engineers visit. You could wait around here, possibly for days, until a member of the Forum Team come along and arrange something for you or you could phone it in ... 150 from a VM phone (free) or 0345 454 1111 from any other phone.
is that something they need access to my house to do, or can they visit my local cabinet to fix.
bearing in mind that my internet has been good for a year or so, what would cause these levels to go out of range
In theory it can be done without access to your home. It's possible that an installer has moved your cable to a different tapping point while doing someone else's installation. The tapping points in the street cabinet are in tiers ... higher powers at the top, decreasing downwards. The simple solution would be to move your connection to a lower powered tapping point, if there are any free. If none are free, the next and less elegant solution is to fit a small attenuator in line with the cable where it enters your hub and home access would be needed for that.