I'm in the same boat. Virgin are supposed to be installing broadband at our new property on the 2nd February. Our purchase has been delayed and we will now not be in until the 12th Feb. I have tried to contact Virgin but can not get through. So they're likely to turn up on the 2nd to install it, only to be met by the current vendors who will no doubt be annoyed.
Really shouldn't be so difficult, never have these issues with Sky.