Interesting link! We agree on Home Establishment!
Salvage ... of course! There would have been massive effort involved in that area, on the battlefields and in the rear. And your Repair Park leads naturally on from that. And regardless of Trade, there was a lot of manpower available to that essential task. I could guess, as a Wireless Operator, he could have indentified what was potentially repairable and what was just junk.
There’s so much focus on the poor sods who had to do the fighting, that the ‘rear echelon’ get forgotten. I’ve recently read (on Kindle) the memoirs of a soldier who spent the War loading and unloading, by hand, tons and tons and tons of stuff in work parties. ISTR he was Non-Combatant Corps.
My grandfather was a Leading Air Mechanic in the RNAS (later RAF!) who seemed to have spent the War repairing aircraft, with 9 Sqn RNAS but often at Dunkerque and other places. I still have his pipe [hallmarked silver band] , on which he carved all his locations. I smoked it for many years, until a crack in the bowl made me decide to preserve it as family history.
Furnes 1917, Bray Dunes, Dunkerque and a few other places.