You need to get the advice of a Lawyer, not a forum, yes there are people here who will have some or a lot of knowledge but unless they see the paperwork related to the aircraft then they really can't help.
I can't stress the need for you to get a lawyer to look into this, you could be opening a whole can of worms into not only the ownership of the aircraft bu the operation of the club, especially if it's registered under OSCR.
Fats