Alexander, you'll love this.
Take a
look at this document.
BT explain that they dropped cookies, but don't tell ICO how, or why (the 2006 report tells you it was done to circumvent the BT terms and conditions that would have prevented them dropping cookies).
They then swapped the 'default ad' (they don't mention it was a charity advert) for a targeted one when possible.
They estimate 15,000 cookies users PER DAY.
There's almost nothing about the 2007 trial.
And BT seem surprised by the idea it should be opt in.