A covenant or agreement, whether contained in a lease to which section 30C (implied terms) applies or in an agreement collateral to such a lease, is void in so far as it purports—
to exclude or limit the obligations of the landlord or the tenant under section 30C, or
to authorise any forfeiture or impose on the tenant any penalty, disability or obligation in the event of the tenant enforcing or relying upon the obligations of the landlord.
A covenant or agreement, whether contained in a lease to which section 30D or 30E applies or in an agreement collateral to such a lease, is void insofar as it purports to modify the effect of section 30D(3) or 30E(2).