Bang goes innovation
Some of the recent and upcoming - and legal - innovations for use of our higher speed internet connections include commercial streaming TV - these uses are bandwidth intensive (especially when we want HD!)
Moving to a PAYG basis for broadband seems like a backward move for the entire industry, as these sort of applications become more expensive, less likely to be adopted, and thus do NOT become the "killer applications" users can use to justify their expenditure on the higher speed links.
Sounds lie shooting themselves in the foot to me.