Where in consequence of any survey, review, further review or special review begun under any of the provisions mentioned in paragraph 22 above two or more definitive maps and statements are prepared whether before or after 1st April 1974 for different parts of a new county, the county council shall not take any further steps under those provisions in relation to those maps and statements until all such maps and statements have been prepared for the whole of their area (less any part of it excluded by paragraph 27 above).