I have the opposite experience of NTL, have always had a tech out with three days who have turned up and resolved the issue, installation was three days after i rang looking for the service and i always get discounted if my service is down for the period of the Outage.
What's the alternative, get a Landline or Overpriced Wireless. I recently moved to a Chorus area, both UPC Companies, install again was in two days and needed to tech visits and broadband was still not working, in the end i had to fix it myself as there tech didn't have a clue so i know where your comming from.
What don't you call pretending to be a new customer renting the house and see if that changes anything.