According to Cable.co.uk this is a feature of TiVo that I hadn't seen before
"What sets the new virgin TiVo box apart from other digital video recorders is the ability to scroll backwards through the onscreen viewing guide and record programmes that you may have missed from the last 7 days. This really is a quantum leap in TV technology and will completely revolutionise the way in which we enjoy our favourite programmes."
and later in the same piece
"Chief amongst the new features is the ability to record programmes you have missed. Users can scroll back through the electronic programme guide up to 7 days into the past. Programmes are then retrieved and stored on the TiVo’s internal hard drive for you to watch when you are ready."
Source
http://www.cable.co.uk/guides/virgin-media-tivo-guide/
If true, this is a really useful feature.