I'm in a similar situation.
My tv and broadband all work fine but following a fire at my property I'm having to move in with my partner. She already has the same package as me so I spoke to Virgin Media and they said that if I cancel I have to pay the remaining six months. Obviously if I move the service with me, she'll have to cancel hers and be left with the same cost for cancelling.
Having spoken to them over the phone, theyve contradicted themselves so many times and although the service here is fine, it seems that if things don't go their way they really dont have a clue what they're talking about.
Since I've been packing for the move, I also found my contract that I hadn't signed or returned so I sent an email which was, in effect, asking them to consider an alternative given my circumstances and that I am unable to take the package with me. As a little treat, I added at the end of the email that I still had the contract here and that "I assumed the 12 month subscription was optional as I received it after I'd been connected and continued to retain the service without completion of any agreement"
I'm hoping it appeals to their better side (if they have one) so I'm waiting on a reply.
A few people have said that the easy way out is to say that you're moving house and using the postcode checker, give them an address that is unable to receive Virgin Media.
But they probably have a response for that. The reason its so hard to get out of these things is that to cover their installation costs, they have to make sure they get at least 12 months subscription from us.
Don't give up!