Not necessarily an offer of help I'm afraid as I'm up to my eyeballs in it at the moment as far as work in concerned.... but what would be the first part of your post code? Or to ask another way, is your ntl account number an 8 digit number starting with 5?
If this is the case I almost certainly know what the problem is, and will at least be able to give you some advice on here of what you need do to get the problem sorted.
BTW hi,
to Cable Forum, hope you hang around.