Thanks weesteev.
Done some digging and found that DOCSIS stands for 'Data Over Cable Service Interface Specification'.
This article from last February says that it will create 'virtual customer services equipment', which I take to mean the STB will be replaced by the cloud, but adds that as this will require a new modem, VM will start with the customers paying for the highest broadband speeds:
https://www.ispreview.co.uk/index.ph...3-1-plans.html
Someone who sits on a working group says to expect it to start happening circa 2021.