Hi Mikey. When (if) you signup to ntl, they supply you with a Cable modem. All you will need to buy is a 4 port router (not an ADSL one!) they only cost about 35quid now.
When you get the router, it will have 5 ports. 1 for the WAN, and 4 for the LAN. You connect the ntl supplied modem to the WAN, and your PC to a LAN port. If you have an XBOX, connect that to a LAN port as well.
That's basically it. The router should detect your cable modem and set it all up for you.
I must also point out, that in general practise, I have found ntl's pings are much lower than ADSL ones.
For an ADSL v Cable comparison, see my site here:
www.dslzoneuk.net/adslvcable.php
Overall, i recommend cable as a far more attractive offer, and less hassle with messing about getting activated and setup for ADSL (which could fail)
I think most people would agree with me that when their ntl connection is working normally, the speeds are very good
Whereas with ADSL, it all depends on the quality of your telephone line.
James