Consumers taken for ride!!

I bought a defy steam iron from PnP Dundee last year July and in November I had to return the iron because it wasn't steaming and required me to iron my uniform twice..I went to the store and was assisted with a return and refund. At that time because I needed an iron I bought another similar defy iron. To my surprise the iron did exactly the same thing and the steam button was totally faulty with this one. I went to the store on Wednesday afternoon and Maria the supervisor told me that,all faulty appliances are sent back to the supplier for checking and the supplier will decide on the outcome! I left my details as she insisted things have changed since the last time I was there! Yesterday around 10 I received a call from the store that the feedback is back and that i should come get another iron! How is possible that from 16h00 the previous day at 10 o'clock the supplier has feedback already?? There's no Defy in Dundee wich proves to me that they're making this all up! Since when are we not allowed to receive refunds on faulty items that no longer needed as they no longer serve the purpose and inconvenienced me the whole time!! What must I do with a 3rd Defy iron when I've already had problems with the previous 2 I bought from them!! I already bought a reliable iron and I want my refund!!