Impossible to say Presario (construction issue). If your building has existing wiring then it shouldnt be an issue, there's a chance your flat is internally wired but if not then the cable will be run externally.
If your area is mostly MDU's and there are existing customers then I dont think anyone will consider it a nuisance as it would be a common occurance to have Virgin installers around the street.
Service is delivered in one of 2 primary methods depending on where you live. Your service will either run from a slotbox in the footpath or from a Cabinet. That cabinet will either be located on the footpath at the entrance to your street normally, or if the building is prewired then the cabinet will be located in a riser cupboard or comms room.
Hope this helps, give me a shout if you need anymore Info or help.