Unfortunately, I think you might have a problem if you continue with BTecs. Level 3 Extended Diplomas are recognised in the Netherlands (no other BTecs are, only this one) but in most other European countries, the situation is less clear. Technically, if you can prove that a qualification is good enough to access university in your home country, it ought to be good enough to get you in abroad but this is not as clear cut as it sounds. It might be worth submitting a UCAS application in order to prove this, even if you have no intention of studying in the UK.
I think you would probably be fine studying at a private university in Poland, particularly those teaching in English. If you are looking to apply to a public university in Poland, the situation with Btecs will probably be a lot more complicated. I suggest that you reach out to universities to see what they have to say but I would not be hopeful of getting an answer in time for you to make a decision about switching to A' levels.