Just to add my £0.02:
I use NTL. Currently it is £18 a month for 1 Mb/s, and I am not aware of any download limit.
You connect through ethernet or USB, Ethernet is recommended, but if you have to use USB, the modem they give you is supported under Linux (uses the module cdcether).
Disadvantage is that you probably need Windoze to get started in the first place. I made the switch after I started Broadband, so this didn't affect me. If you have access to a copy of Win98SE, you can get it started, then delete it and install linux?
Bad side of NTL: Although on the most part their service is pretty solid, when it does go wrong, customer service is poor.
My overall advice to anyone wanting Broadband for Linux is this: Find out what device they use to connect you to the internet. Ethernet and Firewire depend on whether the Ethernet and Firewire interfaces inside your computer are Linux compatible. They nearly always are.
However, USB connections depend on whether the external device is compatible with Linux. So you need to find out that it is.
Once you have this information, you can weigh it up with the other pros and cons.
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