I'm having exactly the same problem actually.
The phone's been dead for 2 days now, I've checked everything. Thing is, I am not really willing to ring up NTL using my mobile (0800 numbers are virtually premium rate numbers when rung on a mobile).
So, I try to report the problem online (my broadband and TV is working fine) and as reported, the link to an fault report email comes to a dead end. I notice it only comes to a dead end once you confirm there is a fault - I suppose they would want to talk to you and check some things - but the phone isn't working so???
A callbox would be the answer (are 0800 numbers free from callboxes?) but the operator would probably demand you be in front of the phone to check things. So only a mobile call at premium rate will do.
I left an email explaining the fault via a different route - I had to lie and make out it was just a query.
God I hate the NTL website - it's like a maze of dead ends and useless information.

(not like this beautiful haven of logic and sanity)