Write to your ISP
Anyone reading this and being concerned, regardless of their ISP, should write a good old-fashioned physical letter to the Managing Director of their ISP. In my case, as I'm with PlusNet who haven't yet decided to be Evil (but who haven't, as far as I can tell, clearly stated their intention of remaining in the Light), the letter reads, in effect, "The day I receive reliable, verifiable information that PlusNet has gotten involved with Phorm or a similar service or interception mechanism would be my last day as a PlusNet customer. Please reply stating your unequivocal intention not to go down that route and referring me to your public, published commitment on that score."
These are for-profit enterprises. They think they see profit in this. Make it clear to them that they're wrong, and that's an end to it. If every ISP in the UK did it, well, then we'd have a different problem and we'd have to band together to form our own. I just don't think that's going tohappen.