You're *always* using a proxy*.
If you don't have one manually specified in your brower's settings, then you still use one anyway, but "transparently".
Bit about proxies:
http://www.cableforum.co.uk/board/article.php?a=14
On the CF toolbar, go to "Quicklinks" on the right, & then "Connection Information". This will tell you if you're using a proxy or not.
*Unless ntl have turned your local ones off for some reason. Happens sometimes.