I don't think NTL:Telewest have an obligation to contact customers about new deals that *might* save them money. It's up to the customer to check the current prices and deals. NTL:Telewest don't exactly hide such information. They change their deals periodically as the markets dictate - why should they constantly inform all of their customers of it?
Everyone got a special "new customers only" deal when they first signed up. Why do these people forget that? Deals change...live with it. You got your "new customer" deal when you joined...why keep whining about what the latest deal new punters get? You've had yours...move on.
I have never felt "ripped off" by NTL:Telewest...they did pester me at one time to take a landline and they say it would save me money. My ignorance told me to ignore, their persistence taught me to actually count. So far, the £30 I spent on having landline installed has saved me approx £95 over what I'd have spent without it. So sometimes they do actually tell you of new deals, if only you aren't as ignorant as me to study them.