That's funny. Litterally.

Virgin Media are pressing ahead with ever-faster services without upgrading the network. The idea of being able to use anything remotely connection-sensitive on a VM connection is a joke. 21CN? Sure, you can establish priority connections. But the high charges (more than you'd pay for the phone call!) are the joke there - and without the charges, you're stuffed since they'll be shaping anything you don't pay for (to make up for the vast additional costs to ISP's 21CN applies).

The future isn't VoIP at all.