Quick note - www in front of the server name doesn't mean it's inside or outside the Virgin Media network, it's just a commonly used naming convention for... World Wide Web be it on port 80 or port 443.
Can I suggest that a better test of the speeds is to use
ftp://gamefiles.virginmedia.com/ rather than http, ftp is a more efficient file transfer protocol, amd it stands for file transfer protocol.
As far as speed tests go, while Virgin Media would have you use a test inside their network I would consider using
http://www.speedtest.bbmax.co.uk it has in my experience always been spot on and is
not on the Virgin Media network so will give a better idea of real world speeds incase you might want to access something outside the VM network, it also measures upstream which a download from the ex-Telewest FTP server will not. speedtest.net is a bit wobbly partly due to the variable quality of the servers it runs on and partly due to the interface it uses.