I am currently doing a project on the Estonian War of Independence and specifically the contribution of the British Baltic Fleet which was there between 1918-1920. I mention that as, I'm aware it's a rather small window and minor event shortly after WWI ended and consequently I'm struggling to find primary sources concerning it. I am a current university student so have access to websites such as JSTOR through my university's subscription to these data bases. Any recommendations for places to look or perhaps even sources would be greatly appreciated.
The first thing you want to do is find the most recent books on the topic. That involves a library search. If you search your system for "Estonian War of Independence," you will find a few books, and even fewer in English, but they are all in around the DK section, specifically DK511 .E6
I would grab these books (if any) first, find the sections on British involvement (if any), and then check the notes for those sections. From there you might be routed to first-hand accounts (diaries, official Royal Navy accounts, etc).