As for the Mark III helmet, I suspect to be fairly common in the non-assault elements of the division, but perhaps Ed or Roger Lucy can answer with more clarity. I haven't seen many photos of the supporting units of 3 CID, to be honest. The RCE and RCA wore Mk III helmets, but they were officially combat arms. Haven't seen many photos of the supporting elements. RCAMC personnel have been seen in Mk III helmets also. If the issue of the British helmets (which the Mk III was) extended to RCEME, I honestly can't say.
As for the CANUCK project - I have done some preliminary research and sourced some photos but my interest is, to be honest, waning. My collection has gone into storage pending a purchase of a house - which may or may not take place in the next year or two. I have more ideas than time to realize them, and other projects in the pipeline. I have definite ideas for formatting and at least a couple of ideas as far as publishers go. A pity that real life stands in the way - but I appreciate the interest.
I'm still waiting for AN OFFICER AND A GENTLEMAN to make it to the shelf before I commit to any other publishing projects. I'm currently looking at some projects dealing with 1960s, 70s, 80s and 90s era tactical board wargames and the community that grew up around them - all games at the tactical (platoon) level, dealing with "modern" (1914-contemporary) period.