1. In this schedule, a new hereditament is a hereditament which comes into existence by virtue of–
(a)property previously rated as a single hereditament becoming liable to be rated in parts, or
(b)property previously rated in parts becoming liable to be rated as a single hereditament, or
(c)a hereditament or any part of a hereditament becoming part of a different hereditament,
and an “old hereditament” in relation to a new hereditament is any hereditament from which it was formed in whole or in part.