Wes,
You will be glad to know that I still have "your" C1 SMG within my collection, along with the full EIS and spare parts kit. The gun has been refinished, and now looks Cdn Arsenals Ltd factory-fresh

The only down-side is that unless the latest sensesless "edict" from the firearms bureaucracy can be reversed, it will be legally fired for the last time on 22 May using my final, valid Special Authority to Posses permit....
As an interesting aside, I have been able to determine that there are indeed only 3 converted-auto C1 SMGs in private hands in Canada - the one you sold me those many years ago being one of the trio. I have tracked down the owners of the other two SMGs which were listed on the importation invoice from SIDEM. No one else has stepped forward to claim ownership of a C1 not on that invoice. Aside from the few additional 12(2) Full-Auto C1s still in grandfathered hands, it would seem that they are a rare Canadian collector's item indeed.
In addition to the points noted in your post above, the key difference between the C1 SMG and the British Sterling is in the method of manufacture. In keeping with the simplified (and therefor less expensive) manufacturing techniques employed for the C1 SMG, all of the permanent receiver parts have flanges which are spot-welded to the tube. In comparison, the Sterling has smooth, seamless welds without the flanges. The more sophisticated (but time-consuming and needless) welding employed on the Sterling gives the C1 a much more "utilitarian" appearance when the two are compared side-by each. The C1 SMG also employs more sheet-metal stampings than the Sterling does - the Trigger Mechanism Housing being one case in point.
The C1 SMGs / Sterlings are great little sub-guns, and are unquestionably one of the best (if not the best) 2nd-generation SMG designs. Having said that, they are now decidedly obsolete in the context of military service for all of the reasons previously noted. Even within the SMG genre, the C1/Sterling design must accede to the more refined 3rd-generation (telescoping bolt) and 4th generation (system-based) designs. The Uzi would be the most prolific of the 3rd-gen designs resulting in a more compact package due to 2/3 of the barrel length being contained within the "over-hung" bolt. The ubiquitous MP-5 is the best-known (and most popular) of the 4th gen designs, featuring extensive commonality of handling drills, parts, and accessories with its rifle-calibre siblings. Owning both an Uzi and an MP-5, I would unquestionably choose to carry either of those in preference to a C1 SMG or Sterling.
Just my $.02 CAD....
Mark C