I've read that M-1917 .45's and M-1917 Enfield .30 US rifles sent to the UK then were marked with a band of red paint on the barrels to indicate that they were for non-standard CTGs. The average Englishnan knew very little of small arms. Heck, you can hand a .303 and a .30/06 to most people here and they couldn't name either CTG. without reading the headstamp. Given military headstamps, imagine the added confusion!
I think most of those arms were used by the Home Guard, but one book said that Colt M-1917's saw some use with the Indian Air Force during the war. If so, they may well have also had some S&W's. Don't know if they were issued to aircrew or ground forces. The priority was to get .38-200 or .455 revolvers in the hands of front-line troops or combat pilots. That simplified ammo supply in war zones. Churchill insisted that his newly-formed Commando troops use the Colt .45 auto as standard and they bought many before Lend-Lease began. Some paratroopers also used .45 autos. Later, 9mm Brownings made in Canada became common among Airborne forces. Colt .32 autos were issued to SOE and other special operations and Intelligence personnel, too.
All of these have been sold as surplus, except for the Inglis-made Brownings, I think. Some of those mysteriously turn up in this country, though. It is my understanding that Canada is looking for a new pistol, and that they will destroy those Brownings!

However, they remain in use for now in Afghanistan.
Keep in mind that in WW I, both Colt and S&W sold .455 revolvers VERY similar to the M-1917 to the Commonwealth nations. These could easily be confused with M-1917 .45's.
Also, Britons with suitable licenses after 1920 (nasty gun law passed then) owned personal .45's of various makes.
I got the impression from a post above that someone thinks that P-14 .303 rifles were made in Britain. I believe that they contracted for all to be made in the US for them. The Pattern 13 .276 experimental arm that was its immediate ancestor was, however, made entirely in the UK, in quite limited quantity. The arrival of war in 1914 scrapped plans to make the .276 the new service rifle, and the SMLE acquitted itself very well in the war.
I am truly baffled by how few American gun enthusiasts seem not to know this basic stuff that I learned in my teens. Maybe I just read more about British matters because of the glamor/glamour of the days of Empire and that being my ancestry. ?? I hope this interests those here who are so often puzzled by such matters.