And I wonder what NTL would do if lots of people were downloading 248Gb a month?
... ah but they can't
Zen will do the same as the likes of PlusNet though ultimately (and Plus aren't the first). No ISP can ultimately provide a truly unlimited service free for P2Pers to download at max capacity and also promise a near to 1:1 experience like most the heavy "downloaders" seem to expect for a consumer broadband product (even at NTL's prices).
I don't really see the problem really. These issues only affect a very small minority who really are expecting a level of service from a consumer product more akin to a business level product.