Any cabling up to and including the STB/SACM is the property of NTL and should not be modified. Contact your local CS team to arrange an engineer visit and avoid any nasty repercussions if the levels end up all wrong and causing problems for yourself and those around you.
Alternativley invest in a router and just run some cat5 instead or use a wireless router and avoid any cables.
adit: see
http://www.cableforum.co.uk/board/sh...9&postcount=10