It'll be either an NTL 200 (silver and black, which I have) or an NTL 250 (blue and black, slightly newer model). Either way, both will do an excellent job.
More importantly than the cable modem itself, I suggest you use these instructions to setup:
http://www.cableforum.co.uk/board/article.php?a=13
The NTL broadband installer CD is the most useless piece of crap I've ever encountered.