Reply to Hamilton: AFAIK, the UK Freedom of Info Act applies only to government departments, local authorities, police, etc. BUT the Data Protection Act applies to any organisation, company, etc., that keeps 'searchable' personal data (whether in computer or written form) on individuals. Never been a JW but from what I've read the records they keep would certainly fall into this category.
Any organisation, company, authority, etc., that wants to keep such info must register with the office of the Data Protection Registrar and specify such things as what data they want to keep, what use they will make of it, who they will share it with, how long they will retain it, etc. There are also rules about not using it for unspecified purposes and so one. The purpose behind this is so that anyone considering giving personal data can check to see how their data will be used, etc., and the Register is open to the public.
I don't know (but I'm sure others on this board do) what the legal position of JW groups is. If each congregation is a separate legal 'entity' (and I assume if, for example, they hold the deeds to their premises then they must be) each congregation would have to register separately. More likely, there would be an 'umbrella' registration on behalf of WTBTS (UK) or whatever the overall UK organisation is.
Under the legislation it is an offence to fail to register, to use data other than in accordance with the registration, and any individual has the right to ask the company/organisation what data is held about them and how it has been used. Failure to comply with a request is an offence.
AFAIK, JW organisations would not be exempt from this legislation.
You have sparked an interest, and I will research further.