Well, i've just received a letter from Gar? Branson telling me that he's putting up my bb, tv and phone package by a few quid, for me, £2.50 a month.
Now, according to their terms and conditions, if they increase the prices, then you can terminate the rest of your contract.
I'm no legal eagle, and going on the 0845 fiasco with mobile phone companies last year it sounds possible
The t&c's are at http://allyours.virginmedia.com/html/legal/oncable/terms.html
and the part I think is relevant is section J, paragraph 5.
Possible, but someone out there will know better than me.