Ring VM and select the 'thinking of leaving' option. You will get through to Retentions (who do a lot more than just try to retain customers). Explain that to them and ask them why the increased charges. If they say that is right, ask them for a better deal.
Are you sure they're actually going to withdraw your TV service? They are phasing out older TV boxes and offering upgrades but AFAIK no-one is being forced just yet. Plus, they're only offering an upgrade to one box per household, so if you have two older boxes only one is replaced.
T&Cs on the upgrade page state: "You can only upgrade one of your old TV boxes for free. You'll be swapping your V+ or VHD box (if you've got two boxes that are the same model, you'll get to choose)."
I have one of the affected boxes and haven't received any communication as of yet.