Is this true?
Yes. Always. A noticeably better rate.
And do you have to take Pounds a Sterling cash as opposed to buying Zlotys with a UK debit card?
Kantors change cash. Maybe a few accept cards, however I've never anyone using one in a Kantor.
Also, the bank machines in Poland accept UK debit and cards (Visa and MasterCard) and give a reasonable rate. MasterCard better than visa. They do usually (unless it's a Halifax credit card and a couple of others) charge a £2.50 transaction fee, so best to just use once and take plenty out. Still much better than changing anywhere in the UK. Some machines offer you the
Also (and this is the same the world around) don't change at the airport. If you need some for a taxi, just change a bit or use the cash machine in Arrivals. Some machines offer you the choice of accepting a guaranteed fixed rate - never, ever choose that option unless you expect the pound to collapse overnight! The normal rate is better. It is a scam run by the banks and there is plenty money saving expert for example) on the internet about this.
If you want to change at a Kantor, have a look at several (in the city centres they are close) and choose the best rate for GBP - kup
means buy (i.e. how many zlotych you'll get, sprzedaz
means sell, i.e. how many zlotych a pound will cost you.