The HLI and Royal Scots Fusiliers merged in 1959 to become the Royal Highland Fusiliers, so if the source of info for his being in the HLI is a newspaper article from 1961, I would suggest it is entirely possible he was in fact in the Royal Scots Fusiliers, particularly since it seems the HLI were not in action against Japanese forces, whereas the Fusiliers were.
Correction, I just read the post above again, and I see the POW camp was from the newspaper article, but the HLI part was from the marriage register, so maybe not.