Moved to computers and IT forum.
Right.. Done that..
Now,

to Cableforum.
We actually have an article that should help you a lot (it was written about NTL, but should apply to Telewest as well).
Assuming it is a true Router, you could have (theortetically) hundreds of devices connected. It should certainly cope with two.
Have a look at
http://www.cableforum.co.uk/forum/article.php?a=39
When you have it working, it's also worth having a look at
http://www.cableforum.co.uk/forum/article.php?a=12 to find out how to secure the network.