it is against virgins terms of service to connect any equpment not supplied by virgin media to the virgin network and if cought you could face legal action and they would morethan likely disconect your home from their network, even if you buy virgin media services
but......
you can get a box called the starview hd combo plus (+) and this can be shipped with either 2 hd digi sat tuners, 2 hd digi cable tuners or one hd sat and one hd cable tuner) so you could watch hd digi sat and hd digi cable on the one box
not sure what the deal is with card slots, ideally it would have a slot for each tuner but i doubt it would tho
google the starview hd combo + and see what it says
i think the price ranges from the £250/£288 upto the £350/£400 mark with a choice of the 2 tuners deppending where bought from
regards
smoggz