Take some of your English money to a bank/travel agents/foreign exchange booth and ask them to change it for Polish Zloty. Always be polite too, it doesn't cost any extra.
Make sure you get the new notes anyway Did you read about the fella that went on a crucial business trip. After taking the clients out for the evening and running up a bill he paid with his Zloty and got laughed out of the joint. They had given him OLD money and he had taken the equivilent of 25p out with him, after raging inflation they moved the decimal point a few places for todays rate,,,,,,,,,he got the old notes that he could have wiped his bum with,