I recently bought a USB keyboard which no longer worked when I returned from my holiday. I called PC World and explained that the equipment was faulty and asked if they had another one, as my journey would be over 80 miles. The chap said yes they had one but could only exchange it if I had the original packaging.
It took me a while to persuade him that (irrespective of my rights or lack of them) he could just simply re-use the packaging from the exchanged item.