"...nominated by the Full Council and me being formally accepted at the next meeting of the committee by a members vote." If you're using the model standing orders, the Council appoints members to committees. There's no nomination and vote process. This procedure should take place at every Annual Meeting, so all members join their committees at the same time.
The legislation on resignations is open to interpretation, but I'd suggest you inform the Chairman of the Council, not the Committee, as the Council is responsible for committee appointments.