An agreement between the landlord and a tenant claiming to exercise—
the right to buy,
the right to acquire on rent to mortgage terms, or
any such right as is mentioned in paragraph 2(1) or 6(1) of Schedule 6A (redemption of landlord's share: right to make final or interim payment),
is void in so far as it purports to oblige the tenant to bear any part of the costs incurred by the landlord in connection with the tenant's exercise of that right.