The parties to a lease shall not be entitled to disapply any provision of section 4 or 5 of this Act from it.

Where circumstances have occurred before the commencement of sections 4 and 5 of this Act which would have entitled a landlord to terminate a lease in reliance on a provision in the lease or on the ground that the circumstances constituted a material breach of contract, but the landlord has not before such commencement given written notice to the tenant of his intention to terminate the lease in respect of those circumstances, he shall, after such commencement, be entitled to terminate the lease in respect of those circumstances only in accordance with the provisions of section 4 or 5 (as the case may be) of this Act.

Nothing in section 4 or 5 of this Act shall apply in relation to any payment which has to be made, or any other condition which has to be fulfilled, before a tenant is entitled to entry under a lease.