8Membership of bodies corporate etc.
(1)A State is not immune as respects proceedings relating to its membership of a body corporate, an unincorporated body or a partnership which—
(a)has members other than States ; and
(b)is incorporated or constituted under the law of the United Kingdom or is controlled from or has its principal place of business in the United Kingdom,
being proceedings arising between the State and the body or its other members or, as the case may be, between the State and the other partners.
(2)This section does not apply if provision to the contrary has been made by an agreement in writing between the parties to the dispute or by the constitution or other instrument establishing or regulating the body or partnership in question.