i've done Ancestry and 23andme tests (and uploaded my Ancestry results to Myheritage. I was b 1948 and adopted so I'm trying to discover who my father was (I'd already found my mother) so I wasn't doing tests for my ethnic origin but in order to find a close relative and hopefully trace my father from that. My birth mother wouldn't say who he was and what she did say might not be true. Her family have been in England (Northumberland/Cumberland/N Yorks)for several centuries and back in 1600s there was some Scottish and Irish input but the tests surprised me- i'm 50% East European. All 3 sites seem to focus on Poland as most likely.
Former Prisoners of War and workers from Eastern Europe who had fled from there (from fascism or later from communism) or fought in the Second World War for the Allies were employed as farm hands on farms in northern England near where my mother lived (Northallerton) and worked (Scarborough) for some years after the war ended. This has made me wonder if my father could have been one of these workers. Another possibility is that my father may have been a US serviceman with Eastern European heritage, maybe his parent/s had emigrated to US. I say this as there were airfields near where my mother lived and at this time it was the end of WWII and the beginning of the Cold War. Obviously anything is possible but those scenarios seem most likely.
So at least DNA tests have given me a clue if not the answer I was looking for.