3. Where any land is used temporarily or permanently—N.I.
(a)for the exhibition of advertisements; or
(b)for the erection thereon or attachment thereto of any structure used for the exhibition of advertisements;
and the land—
(i)is not so used under a right which is a separate hereditament from the land; and
(ii)[F1either] is occupied for any other purpose and rateable in respect thereof[F1 or is not so occupied and but for that use would be rateable under Article 25A];
the net annual value of the hereditament comprised of or including the land shall be so estimated as to include the increased value arising from that use.