People who buy leased lines for hundreds, sometimes thousands of pounds a month only get bandwidth guaranteed to their ISP's network. So the point (as should be obvious from the post I was replying to!) is that if Virgin hosted their own speed test they could then offer more accurate speed tests.
I know speed test is rubbish for me. I get full bandwidth on torrents and usenet but not on speedtest.net. If I didn't have access to usenet/torrents I'd be moaning that I'm not getting the speed I paid for just like alot of VM users do.