Also - pyrlandia-boogie.pl in Ostrow Wlkp.
I know someone who has done a lot of jumps with them and is very very happy, and they've also done tandem jumps with two of my friends (me, I stayed on the ground) - who were also very happy. I can attest that they're very nice people there.
Failing that, do you know if there are any kit suppliers based in Poland? I'm just wondering whether a rig purchased abroad may save me some money as they're jolly well expensive over here.
Don't take my word for it, but from what I've been told, it's hideously expensive in Poland too.