This Act shall have effect subject to the modifications specified in Schedule 8 to this Act.

The modifications so specified shall cease to have effect on such day as the Secretary of State may by order made by statutory instrument appoint; and the Secretary of State may prescribe different days for different modifications specified in that Schedule to cease to have effect and different days for the modifications specified in paragraph 3 of that Schedule to cease to have effect in respect of different classes of vehicles to which those modifications apply, or may postpone or defer the cesser of those modifications in respect of any particular class of those vehicles.