Hi andycambs
Do you still have two 360 boxes as per < this post > ?
If so have you tried swapping them around to see if the error(s) follow the box?
The CS3300 < fault help page > suggests turning the box off at the wall and checking the cabling, then if the issue persists to contact VM. In the past that help page suggested it was just a temporary issue.
Does this error occur on live TV, or only on catch up, on demand, apps or recordings?
If you do still have two 360 boxes and it's occuring on recordings then ensure both boxes are turned on, and set to either Fast Start or Active start mode so the boxes can communicate with each other.
Also when this CS3300 error (or any error) happens have you looked at Check service status < here > at the top of the page? You can also a run a test on your equipment from there? If nothing is showing you could also try the Service Status number 0800 561 0061. This often gives details of more local issues down to postcode level