If ntl and Telewest do merge, then I think that ntl and Telewest should keep what they are strong at, and hand over the part in which they are weak at to the other company.
For example I would like to see ntl hand over their broadband operations over to Blueyonder, so we would get all the benefits of Blueyonder such as no cap, reliable email, upfront no-bull status page etc.
I very much doubt this will happen in practise though, it's probably all driven by profit and I think at the end of the day how much money they can make is probably going to be paramount, above everything else