It's all a case of business organisation and marketing - the basic networks are going to remain in their current form - Like in NTL there are both the langly and bromley platforms - does anyone know if the telewest network is similar/easily converted to one or other of these platforms?
Chances are we'll have a minimum of two networks, probably three - the actual likelyness of the individual networks going wrong isn't likely to change!
That said, the way the rest of the company is run WILL change. policy will be merged, the things like speeds (which have already been kind of standardised) will be negotiated between marketing and technical - there's no point in taking all the good bits (uncaped service, 3meg speeds) if part of the network will collapse under the strain.
As for branding, I must say I had a wee giggle to meself when I thought it could be called ntllywest. It just sounds a bit funny
I imagine for a while it will be called NTL:Telewest, then a big rebranding will be done 6months to a year after the merger, costing about £2milli on. No reason why it shouldn't work, as long as they do it right!