I'm not sure I understand the question, Gordon. The company will (hopefully) gain charitable status. There will not be a new body that is the charity. So the charity and the company will be the same thing and 'guarantor members' of the company will become 'guarantor members' of the company registered as a charity. (At the same time the board members will take on additional responsibility as charity trustees.) Or did I miss something?
That's how I understand it, and I did a decent about of research into the subject.