Hmmm... dvb-c card with a cam reader generally will equal a cable decoder box. There used to be tutorials on modshack.co.uk to build a linux PVR using specific DVB-C cards - The Technotrend range (as opposed to DVB-T for terrestrial and DVB-S cards for Satellite) and software decryption algorithms (for the piraters) or Cam reader (for those with legit viewing card) that'd work absolutely fine with UK Cable (Telewest / Virgin)... the site is now long gone tho (probably due to pressure from the UK Cable companies).
These days, the Nagravision decryption card is tied to the MAC address of the Cam reader within the decoder box (Stb)... so you need to find someway to clone the Mac address of the STB onto your DVB-C card / cam... otherwise all you get are the freeview channels.
See
http://club.cdfreaks.com/f90/decrypt...nal-uk-147051/
Satelco make a HD-ready DVB-C card...
http://www.dvbshop.net/product_info....I--DVB-C-.html
and a breakout CI-Interface for your viewing card -
http://www.dvbshop.net/product_info....DVB-cards.html
All comes down to your cable company and what security they have in place (ie: whether they enforce the use of their STB, or allow use of legit viewing card with a DVB-C - here in the UK, they don't. Everything is locked down, and use of anything other than the STB is a violation of the cable company's T&Cs and they turf you off your contract.)
Note: Technotrend is usually the brand to aim for - s'the same hardware as Hauppage but with a diff sticker on the top...