This post on the Community Forum should help
http://community.virginmedia.com/t5/...elp/td-p/20585 may help
As for cables inside a new flat block, it's up to the developer. Virgin Media will work them to get the correct infrastructure in place at the appropriate stage of the build, but if they don't know it's happening there is nothing they can do.
It's difficult to wire up a flat block after the fact as there is then nowhere for the cables to go.