Much of the problem would go away if ISPs were completely separated from content distrbutors, and revert to being only data pipes,. As it is, though, with BT broadband you'll get slower video from Sky and Virgin channels, with Virgin broadband you'll get slower access to BT sport and Sky channels, and so on.
At the moment it appears that those ISPs are overcharging on basic connectivity to subsidise their bundled content services - admittedly the figures are (deliberately?) obscured, but it seems clear enough.
This is a different (albeit related) issue to separating BT from OpenReach, BTW.
As has been pointed out, the language of the new rules is so vague as to be functionally devoid of meaning. There will no prospect of any legal challenge to an ISP succeeding under this legislation unless it is very substantially clarified. But it won't be, will it?