In particular, did they fight in the territories of modern-day Belarus or Lithuania?
Update: Online sources such as (https://en.wikipedia.org/wiki/Allied_intervention_in_the_Russian_Civil_War#CaucasusAllied Intervention in the Russian Civil War, http://www.nationalarchives.gov.uk/pathways/firstworldwar/spotlights/allies.htmNational Archives UK, and https://www.historyanswers.co.uk/history-of-war/saving-the-war-or-killing-bolshevism-in-the-cradle/ the war or killing bolshevism in the cradle, etc) state that troops were deployed in North Russia, the Caucasus and Siberia. Furthermore there was a British naval force in the Baltic as mentioned by @JohnDallman.
However, I've not yet found clear sources indicating the precise actions and movements of British forces (which are typically described as 'muddled and half-hearted'), and in particular, whether the British presence ever extended to the Southern Front.