Heh. You probably have something interesting on your site and someone wants to be notified the minute your sites gets updated.
I wrote a script that uses Curl (similar to Wget) and it hits my favorite band's web site four times a day and it emails me whenever the concert page is different than the last time my script checked. (This way, I know about concert announcements as early as possible). I've had that script running for three years and they haven't changed their concert page.
If you don't want the guy hitting your page, you could just block him (lots of different ways to do that). You could display a personal message to him everytime he checks if you wanted to.
Telewesst isn't going to care that one of their users is hitting your site once every 15 minutes. (And you probably shouldn't be too worried about it either - it's no big deal. I mean, would you care if he was using Internet Explorer and came to your site once every 15 mins?) Telewest would probably get involved if he was hitting your site 15 times per seconds (that would be abuse) but once every 15 minutes is nothing - some people visit PHPBuilder more often than that!