Nobody has a second cable running back to the cabinet, it's not how cable (and DOCSIS) works.
There is one cable running down the street and each property taps off it.
If I am reading what you have put correctly then this is not how the Virgin Media network is installed around here.
Each property usually has it's own coaxial cable run from the outside of each house (the brown box or grey if from Telewest/Yorkshire cable days) to the nearest street cabinet (RG6 or RG11 coax dependent on distance).
The cable is pulled through the underground ducts using a "Cobra" rodding device by the pre-installation team. The little square (or triangle) access hole (called a Toby box) you see at the end of your drive is where they would rod the cable from lifting up any manhole covers to intercept the cable if it needs to go around corners. They leave the excess cable in the cabinet (or the chamber in front of the cabinet) so that when the installation team come, they can pull the slack out to run through the garden/drive etc.
Although houses usually get their own cable, there are instances on flats and other communal buildings where the same cable will be used (such as no space, not allowed to pull another cable to connect a new customer.
Local street cabinets, are connected to each other by a much large higher quality coaxial cable. This cable is not what you are teed off directly off though. This larger cable will eventually link to a fibre node that sends all data from the interconnected cabinets back to Virgin's core network.