You are correct Gary it is a commercial rifle, as it started off as a commercial " MLE " then converted to .22 the only chance of it seeing or being in service would be, a Officer purchase (when it was .303) or commandeered for the War effort, I,m not really clued up on that subject but am sure others would be.
(I,ve seen a Civillian rifle that was marked to a Local Home Guard unit, but was marked on the butt, (paint) the unit and the owners name, Long gone now and the original owner)
Regarding post #10, was wrong about the sight, I PM,d someone who knows his stuff on them, It's a A.J. Parker model TZ model 1. folder, made in 1928. (Big thanks to Muffer for the info on the sight)
back to the original question, I,d be inclined to go with the quote from TB,