Well, I went for the cheaper £15 a month version three months ago.
The installation engineer completelty ballsed up the hook-up having waited all day for him to arrive.
This meant another day waiting to be re-installed.
This time it worked - but they did charge me from the original installation date.
I have to say though it has been brilliant & I have had no service failures whatsoever since the above was sorted.
I've been with NTL / C & W & Nynex since they started and have to say, if anything goes wrong, you are completely Donald Ducked because they must have about the worst customer service of any company I have ever come accross.
Good Luck