as you say Kymmy, its only against the Virgin Media T&C to connect anything not authorised (to be clearer) by them....
however your comment about "If you're using a viewing card via a DVB-C then it has to be a hacked card" is not quite right,technicly speaking from a contractual Point Of view, your paying for the rental and use of one (or more) devices to decrypt the DVB (Digital Video Broadcast) TV services you pay for.
there are infact ready made matched and available on the open EU markets, paired DVB-C /nagravision CAM suitable for VM use available all over the EU, covered by legal precident to allow any EU resident to connect to your cable supplyer.
so when and if you "give VM a ring and ask them for a card to be matched to your DVB-C card and see what they say
" and they say NO you cant do this, and get it in writing from them to be sure....
you could then if you like, potentially bring a simple "small claim" county court case of "invalid clause" restricting your EU rights for connecting any 3rd party equipment to Virgin Media's cable network to use your valid current subscription.
not that anyone has bothered to do so so far OC, but its an option open to anyone that can be bothered to look at the EU DVB-C cable TV, and free trade laws AFAIR.
for instance to try and drag VM into the legitimate EU 3rd party DVB-C hardware marketplace...