That article you found is almost all wrong. For starters there is no such thing as a no1 mk1. The rifle started as an LE Mk1* (long Lee Enfield) that has been shortened to range pattern. That means it belonged to a civilian range shooter while still a long Lee (30" barrel) and when the SMLE was adopted for rifle club target shooting, was converted to the new 25" barrel, either by replacing the barrel with a new made H barrel, or shortening the existing barrel. Usually if a new barrel, it would have the MkIII (No1 MkIII) front sight fitted. Yours, like the one (as far as I can tell) in the article, had the original barrel shortened and the original ramp forsight re fitted. Of course the foreend was shortened and shaped to take the original nosecap too. The conversions were done at Lithgowbut many gunsmiths specialising in target shooting equipment also did conversions, usually incorporating Lithgow made H barrels with their own name on them, eg; "Motty" etc.
Interestingly, your rifle has a Metford form barrel with Enfield rifling... does it have a serial number on it?
At the outbreak of WW2 a lot of these rifles were handed in for the war effort. What they were depended on what was done with them. The range pattern rifles were used for home defence units as Bruce said above