In section 98(4) of the [1975 c. 72.] Children Act 1975 for the words " or residential home within the meaning of Part III of the Mental Health Act 1959 " there shall be substituted the words " residential home for mentally disordered persons within the meaning of the Nursing Homes Act 1975 or the [1980 c. 7.] Residential Homes Act 1980 " .