18. For the purposes of this Part, each of these is an occupational pension scheme—
(a)an occupational pension scheme within the meaning of section 1(1) of the Pension Schemes Act that has its main administration in the United Kingdom;
(b)an institution for occupational retirement provision within the meaning of Article 6(a) of the IORP Directive that has its main administration in an EEA state other than the United Kingdom;
(c)a pension scheme that is prescribed or is of a prescribed description and that has its main administration elsewhere than in an EEA state.