You may or may not be aware but the Charites Act 2006 is now in force and it means that from end 2007 charites (including the JW's) will have to proove that they offer public benefit if they are to still retain their charitable status and in turn get gift aid on nearly every single donation and keep their tax exempt status.
The charity law association made some very interesting comments regarding the witnesses in their memorandum that was submitted in evidence to the Joint Commitee on the Draft Charites Bill. Their comments on the Taylorite sect of the Exclusive Brethren "excluding children from the family home" is also quite relevant. This is only enidence from an outside body but it shows things could change.
http://www.publications.parliament.uk/pa/jt200304/jtselect/jtchar/167/4061625.htm
They are about to start consultations regarding what public benefit should mean for different charitable sectors, including religion. They are welcoming interested persons to take part and it would be a good way to get the point accross that certain organisations who's actions fall below what society expects nowadays should not have charitable/ tax excempt status. Whilst they are looking at public benifit they are also looking at what detrimental effect charites have and if these are sufficient they will take away thier charitable status.
If any UK people want to take part the link is
http://www.charitycommission.gov.uk/enhancingcharities/pbconsult.asp#2.12
From here you can email your details to take part in the consultation, just make clear you are interested in religious public benefit...