Yes, that would be correct for the wiring connections.
However, the terminations shouldn't be floating around loose behind the plasterboard. The wires should be contained inside a back box, something like this
The plasterboard is cut to accept the backbox with a sharp knife (it needs to be a close fit) the backbox is pushed into the opening and the yellow tabs click out to the sides to hold it in place. [There are other variants but the principle is the same]
A blanking plate can then be fitted to the backbox.
If you fit a metal blanking plate to a plastic back box, the metal blanking plate should have an earth connection to it. Or, have insulating material between the electrical connections and the metal plate to prevent them coming into contact with it. The piece of plasterboard you have cut out will do.
A metal blanking plate screwed to a metal backbox that already has an earth connection doesn't need an additional earth connection, because the connection is made via the blanking plate fixing screws.
