Section 62 through 64 of the branch handbook is their internal data handling policy. It's nothing amazing, but it's on the ARC website as part of the evidence gathered there. Nothing incredibly unusual other than their assertion that they will never destroy data about a person's status as a JW because that's part of their religion to know.
The British specific policy information is contained in letters from 1999/2000. I know I posted a few, and I'm sure konceptual99 (?) posted more too. It gives what the elders actually do retain after notes have been destroyed. It's not a lot. Sure someone can link. My internet keeps dying (BT sucks) or I would repost.