Hi Liz,
By "RNZAF archives people" do you mean the NZDF Service Records people (see link below)?
NZDF Personnel Archives and Medals holds a collection of about 1.5 million service records relating to 420,000 New Zealand service personnel who served in New Zealand’s Military Forces post WWI.
www.nzdf.mil.nz
Given the info you provided, they are the first people I'd go to. If they don't have his Service Record, then the next port of call would be the RAF...which can be a long process. However, let's see if the NZDF Service Records team has his info first.
Have you obtained the 57 Sqn Operations Record Book from the UK National Archives? Here are some links to relevant records that you should be able to download for free (you'll need to register with the UK National Archives but, after that, downloading records is free):
The official archive of the UK government. Our vision is to lead and transform information management, guarantee the survival of today's information for tomorrow and bring history to life for everyone.
discovery.nationalarchives.gov.uk
The official archive of the UK government. Our vision is to lead and transform information management, guarantee the survival of today's information for tomorrow and bring history to life for everyone.
discovery.nationalarchives.gov.uk
The official archive of the UK government. Our vision is to lead and transform information management, guarantee the survival of today's information for tomorrow and bring history to life for everyone.
discovery.nationalarchives.gov.uk
There are other ORB records in the series AIR 27/538 but they are based on individual months, so you'd need to pick out the months when your Dad was with the Squadron.
UKNA may have records for other units in which your Dad served but we'd need to know the specific units...which will probably be found in his Service Record.
Hope this helps a little bit. I wish you every success in your archive hunting.