Well...
The Royal Sussex Regiment were the last to be stationed in Korea, leaving there in July 1957.
GLOSTER MEMORIAL, KOREA, 1957
Maybe the search narrows to either a representative of the RA generally who attended the dedication of the memorial or, just maybe, someone from C Troop, 170th Light (Mortar) Bty.
A bit of interesting reading regarding the chap who wrote the quote above:
NDM Patron & Chairman Discuss Ideas - Campaign News
Looks like 170 Bty was in either Hong Kong or NI in 1957, from
The Royal Artillery Association › Community Forums › Disbanded Units/OCAs › 45 (Fd) Regt › 45 REGT- 1947-1993 AND BTY HISTORY 52,170,94,34,176,HQ
I'm starting to suspect that the British Military Attache to South Korea in 1957 may be the key to the identity of the officer in the photo. The BMA seems to have been Col AEE Mercer MC... according to:
An Almanack...: by Joseph Whitaker, F.S.A., containing an account of the ... - Joseph Whitaker - Google Books
Of course, this may not be relevant...
Hmmm. By 1983, he was a Lt Col. That's curious...
http://himalaya.socanth.cam.ac.uk/collections/journals/bnsj/pdf/bnsj_07.pdf
Now this may just be coincidence, but in July 1959, Major Allan Eric Eustace Mercer was promoted to Lt Col, as shown in The London Gazette:
Viewing Page 8230 of Issue 41905
Most significant is that he was badged Royal Artillery.
I'm tempted to suggest that the chap in the photo could well be the then Major Mercer MC RA who, as Military Attache in South Korea, would almost certainly be expected to attend the dedication of the Glosters Memorial. Maybe he was granted an acting Lt Colonelcy.
All we need now is a photo of Maj Mercer to confirm that he looks like a school teacher.
If you're intent on tracing him, the latest reference that I can find dates from 1976:
http://www.london-gazette.co.uk/issues/46983/pages/10908/page.pdf
(The solicitors may have separated, possibly with two of them operating in Leeds).