Not quite cool. The latest tactic of ISPs everywhere to make more money is to charge not customers, but content providers for their traffic -- i.e. if YouTube wants their site to work fast on your ISP, they need to pay the ISP a certain amount, and then everyone on that network will experience the site quickly. So in this case, Virgin would be asking Blizzard, responsible for all the World of Warcraft traffic, to pay a premium price for customers to receive it quickly. And anyone who knows Blizzard knows they probably aren't too excited about paying such a price -- they'd likely call Virgin Media out for slowing the connection down before paying protection money for their data.
At any rate, it seems like there's a battle coming, and your character's information may be caught in the middle of it. As always, you've got to fight with your wallet -- if Virgin or any other ISP threatens to hold data hostage like this, it's time to find a different ISP to pay your money to every month.