Oh, I should point out that Virgin do have some download limits - depending on the service level you're on, if you download more than a certain amount between 4pm and 9pm (their peak period, apparently), they downgrade your bandwidth for five hours.
For the 2Mb/s level, you get downgraded to 1Mb/s if you download over 350MB
For the 4Mb/s level, you get downgraded to 1Mb/s if you download over 800MB
For the 20Mb/s level, you get downgraded to 5Mb/s if you download over 3000MB
All of these only apply between 4pm and 9pm.