While a disposal licence. . . is in force, then—
and
Subsection (4) . . . of section 5 of this Act shall with the necessary modifications apply to a proposal to serve a notice in pursuance of paragraph (a) or paragraph (b)(i) of the preceding subsection as it applies to a proposal to issue a disposal licence, except that—
Section 5(6) of this Act shall apply to an application in pursuance of subsection (1)(a)(ii) of this section as it applies to an application for a disposal licence.
Where a disposal licence. . . is in force and it appears to the appropriate Agency—
it shall be the duty of that Agency by a notice served on the holder of the licence to revoke the licence.
A notice served in pursuance of this section shall state the time at which the modification or revocation in question is to take effect.