Hello Manxie!
I have also found John James CORRIN listed on the Auckland War Memorial Museum Online Cenotaph. Added to the information found by Averil and Sue, additional info there shows:
Embarkation Details: 26 Apr 1917 - 19 July 1917 to Plymouth, Devon, England HMNZT 83 - Vessel was "Tofua" - Rifleman; 25th Reinorcements J Company NZ Rifle Brigade.
Medical Notes: Nature of Injury DAH - 30% disability - Present Address King George V Hospital, Rotorua (NZ Army List 1920 - Members of Expeditionary Force, suffering permanent disability 20% to 100%)
King George V Hospital, Rotorua was built during the First World War, as a convalescent hospital for returning servicemen, in that area, because of the thermal waters there, considered to aid the healing process. Interesting.
On the same page I have also found an RNZAF WW2 entry for Hal, (Herrold Raymond CORRIN) which I will send to you via email, as there is a lot there. I will be able to go into this site now and register, which will enable me to update details, for John and Hal. How great!
Hope you are well,
Deci