From what I've read they will do some infilling if there is demand from consumers and the costs are low, IIRC £400 per property or something like that.
Virgin Media cop to speed issues with their Super Hub
Users of Virgin Media's new super-hub have been hit by speed problems following upgrades offered to customers on the 20meg XL product. Customers were offered an upgrade to a faster 30meg service with no additional monthly fee, but a one off £30 equipment charge for the new router that virgin dub the "Super Hub". Unfortunately a problem has been found in the new super hub that is rendering it not-so super, and users are seeing speed issues following this.