I have no idea if this will be helpful or not, but you might want to seek legal (rather than Virgin Media's) advice. Under English law, contracts are only enforceable if the terms are reasonable. A legal professional would be better placed than me to decide if requiring you to continue with this lack of service is something a judge would deem reasonable or not. Though I'm sure most people reading this will have their own private opinion.
Second possibility, if you get coverage outdoors, devices are available to boost the signal locally which could give you signal indoors too, google should turn some up, they're not horrendously expensive.