Nothing in this Act--
(a) applies to an action or arbitration for which a limitation period is fixed by or under an enactment other than this Act or by or under an Imperial enactment (not being an enactment or an Imperial enactment repealed or omitted by this Act), or
(b) applies to an action or arbitration to which the Crown is a party and for which, if it were between subjects, a period of limitation would be fixed by or under an enactment other than this Act or by or under an Imperial enactment (not being an enactment or an Imperial enactment repealed or omitted by this Act).