There is a good article about this in this months Computing Which? It would seem that the Information Commisioner's Office is now involved, requesting info from Phorm and from the three ISP's so far involved (BT, Virgin Media, and Talk Talk). Talk Talk it would seem is the only ISP to indicate that its customers will need to opt in rather than opt out. The Consumers Association is also to be involved in discussions about Phorm.
So far my ISP (Orange/Wanadoo/Freeserve) does not seem to be involved.