6No grant shall be made under section 3 of this Act towards expenditure incurred in providing a building or extension in an intermediate area in a case where any work on providing that building or extension (being work undertaken by or on behalf of the applicant) was done on the site before 25th June 1969 ; nor, where any work on providing a building or extension intended for occupation by an undertaking was so done, shall a grant be made under that section, so far as applicable to intermediate areas, in respect of a purchase of that building or extension for occupation by that undertaking.