I literally got my MAC code two days ago, checked the Sky website and it was possible to order SKy Broadband on its own, £12.50 per month and gets me Anytime Plus on my HD box.
From today the website has been changed and I could not order Broadband without taking their line rental. I phoned up their sales line and was told that from 1st September it is no longer possible to order Broadband without taking Sky Talk line rental.
I don't recall having seen this anywhere, so I guess it was not an announced change. Pretty annoyed to be honest, I don't think this is a clever move at all.