Subject to the provisions of paragraph 19(4) of Schedule 15 to the Act, any proposal for the alteration of a valuation list in respect of a hereditament in a London borough shall have effect as from 1st April 1965 as if it had been made for the alteration of the valuation list for the London borough in respect of such hereditament, and any action in relation to such proposal taken by, or in relation to, the rating authority shall have effect as if it had been taken by, or in relation to, the council of the London borough.