I’ve been in Poland a good few times for both work reasons and visiting my G/f’s family. Polish liquids are very cheap, much more so than UK, and pretty decent from what I tried, you can buy them in any of the (ex-state) tobacconist shops that are everywhere. I didn’t see many actual vape stores though, but plenty of places selling hardware, even in supermarkets like Kaufland etc. Not a great selection though. I’d stick with Fasttech/ other China sellers for hardware bargains and just score a load of liquid at a relatively cheap price if I were you.