If or to the extent that there is no such agreement any party to the arbitration agreement may (upon notice to the other parties) apply to the court to exercise its powers under this section.
Those powers are—
to give directions as to the making of any necessary appointments;
to direct that the tribunal shall be constituted by such appointments (or any one or more of them) as have been made;
to revoke any appointments already made;
to make any necessary appointments itself.
An appointment made by the court under this section has effect as if made with the agreement of the parties.
The leave of the court is required for any appeal from a decision of the court under this section.