The British Rifles and French-style helmets are clear enough. I think the web equipment is also British but who are they? I am guessing one of the Baltic Republics, ca. 1919, equipped with surplus equipment to fight the Reds.
I'm sorry, I meant to say LATVIAN soldiers. During their fight for independence from the Russians and German Freikorps, beginning in 1918 the British and French supplied the Latvians (and the other Baltic republics) with considerable military equipment. On his website, Tuco, has several photos of Latvian troops armed and uniformed exactly the same as those in your photo.