Ring virgin cancel your contract and tell them the reason is because the price has become to expensive, and you have found that talktalk are doing, bb and line rental for £18.50, which they are. Within a week you will get a call from virgin retentions offering you a better deal.
P.s.
I've just had a letter telling me they are increasing the price be £3.90 a month in February, so I'll be cancelling as well.
Make sure when you take out your new 12 month contract that there will no increase in February.