Blablaman ...
As you make clear 1400 or so congregations have charitable status and so does the Watchtower Society of Britain. If you're asking via your petition question to have all of these to be removed from the Charities register that isn't made clear on your petition question. If on the other hand you're asking to have the Watchtower Society of Britain removed, again that isn't made clear on your petition question.
Parliament in debating this issue, should it receive 100,000 signatures needs to know to whom the question is refering ... all of the 1400 congregations or the Watchtower Society of Britain? As the religion of Jehovahs Witnesses is not a charitable institution in its own regard. As stated in the Watchtower Society of Britains objectives, their aim is to further the Jehovahs Witnesses who are a Christian religion.
Sifting through the legal jargon and putting into laymans terms ... the Jehovahs Witness religion (to which your petition question refers) is not a charity but a religion, whereas the 1400 congregations and Watchtower Society of Britain are charities on the register (to which your petition question does not refer). Hence Parliament cannot revoke the charitable status of the Jehovahs Witnesses, as they have never had one in the first place.