Sky's equivalent of the NTL PVR has to be Sky+ and as is fact, is free per month to customers on the top package. So, for every tenner a month you pay NTL, you could have a Sky+ box which is miles better with a proper epg and no software cockups.
Over a five year period, here's a summary.
NTL user £600
Sky+ user £0
Should your Sky+ box break you'll have plenty of money left over to get plenty more after your guarantee runs out!
Even more so if this happens
http://www.media247.co.uk/skydigital/news.php
(insert smug wink here)