NTL have a big problem with communication. Having someone on the forums in a official manner can help in a great deal but of course there will be temptation by users to use this as a primary way of dealing with problems, I agree with ian@huth that normal channels should be used first. However if people provide proof they have tried normal channels and problem isnt resolved then the problem can be escalated how can this be done?
Ticket numbers - When customer A rings up and speaks to tech support guy A he tries Tech support guy A solution and gets a ticket number for the problem, if customer doesnt ring back within say 72 hours the ticket can be closed as resolved. If customer needs to ring again they say the ticket number and Tech support guy B can immediatly see whats been tried so far and then maybe escalate the problem further if its ntl end causing the problem or perhaps send an engineer out to customer. If the customer still cannot resolve issue then they just give ticket number to the NTL liason on the forums.
Email notification of planned outages - these could save a lot of headache for tech support as people will know in advance of maintenance and should not need to ring up to ask whats going on and why their service is down, if possible can be done on emergency maintenance also.
Consistent billing - I have a strong belief that staff are either told to pretend that the double billing problems are not an error or they are simply not trained up or incompetant, I am aware their is staff who recognise these problems and reimburse the customer but its not the case across the board

lots of customers end up out of pocket because NTL change them from after month billing to pre month billing.
Offers for loyal customers - every 12 months 10% of a bill or perhaps a free premium channel once a year for a month, it promotes the channel and can tempt them to sign up to it and generates good feeling amongst customers.
Thats it for now I hope others like my ideas