Nor,
I would advise as per the other posters to ring and speak to retentions on the 'thinking of leaving us option' and tell them exactly what services you want and roughly what you are willing to pay.
I've been a little peeved lately with the recent price increase and little to show for it in terms of new channels, etc, but have always been happy with VM's services. As I'm recently out of contract I rang up just the other day, advised them I didn't particularly wish to leave but told them what I wanted and the comparable offer with Sky. They worked out the best price they could offer me for my requirements and I was content to accept and renew my contract for 12 months.
I am pretty sure they would be willing to keep you as a customer too. You don't mention what services you have but if you currently pay £105, you could switch to the new VIP Collection for £103.90 and pretty much get everything they have to offer including your Sky HD channels -
http://store.virginmedia.com/bundles/vip.html
Hope this helps and good luck getting a better deal.