The Polish authorities certainly accepted UK theory exams last year, whether this is still the case I don't know, if as you say they keep changing their rules.
I had a Polish citizen who was working as a doctor locally, did a few hours flying and all the PPL(A) theory exams. He subsequently could not agree contract terms with the NHS trust, so unexpectedly returned to Poland. I cave him a SRG\1105 (PPL application form) with his exam details on as proof. When he continued his PPL training in Poland, the authority there contacted the UK CAA, who in turn asked me to verify his claimed passes. Once they had confirmation from our CAA, they accepted his exams done here.