Hi Michelle

Quite a lot of information available for your family.
> Chas. Nicholas Robert COUCH - died 19 October 1949
> Rose Campbell COUCH - died 21 April 1952
Cemetery records available at -
http://www.northshorecity.govt.nz/> William Alfred COUCH
There is a record at Purewa Cemetery (Auckland) - shows date of service as "5 March 1974" for William Alfred COUCH.
http://www.purewa.co.nz/However there is also a record for a William Alfred COUCH (died 1974) at North Shore (see earlier cemetery link). I think this is probably the record for the person of same name who was cremated at Purewa - the North Shore record looks like it is a burial of ashes. (Further information is able to be obtained on the North Shore website).
Archives New Zealand (Auckland Office) holds a probate record (which should contain a copy of will) for William Alfred COUCH of Northcote, dated 1974. At Archives NZ (in Wellington) there is a military record for a "William Alfred COUCH" (possibly the person you are looking for ?).
http://www.archives.govt.nz/The NZ Marriage Index shows the following : -
> Charles Nicholas Robert COUCH
Rose Campbell SMITH
Year - 1892 [Folio # 0062]
> William Alfred COUCH
Ruby Evelyn JONES
Year - 1916 [Folio # 4519]
[Archives NZ also hold a divorce record (1930) for a William Alfred COUCH (wife's name not stated) ... there does though, seem to be a viewing restriction on this file] :
Good luck with your search.
Lu