Well, it won't work on your Mac, as it sounds like the Mac is not connected to the NTL Broadband service. They won't let you at your webspace except when you use your NTL service to access it.
As for the PC, at home - well, that's a different problem and I frankly don't have a clue. Hopefully someone else will be along with some ideas shortly. Sit tight!
to Cable Forum, by the way.