CPA has always been a bit of a grey area for most. It either isn't clearly defined, or retailers have found some way of changing the wording to suit themselves.
My only experience with a failed CPA was when I bought a new mouse from BT games in Eastgate. I asked to try it out to see if the shape/weight was what I was looking for, and they refused saying they weren't allowed to open any packaging. Fair enough, I'd return it for an exchange after testing if it wasn't suitable later that day, I said, as I was effectively making a blind purchase. Assistant said fine, and I was on my way.
Got home, took it out the box, and found I didn't like the shape nor weight (didn't take it out of the plastic cover nor did I even unravel the cabling). Packed it up, and went back to the store.
Was later in the day, and the assistant that sold it to me wasn't there. Spoke to a different guy, who outright refused to exchange it, because of anti-piracy rules because they sell games. I was like dude, I didn't pirate the mouse. Still refused, saying it applied to everything in the store - sort of a blanket statement, no exchanges on any items, I can check the receipt, it says so on the back. I quote the CPA, which overrides any company's returns policy within reason, stating that I was unable to test the product in store, so had no way of knowing what I'd bought was what I actually wanted. I ask for the manager, who gives me the same bullshit story. Start losing my ****, and a friend of mine who works in the centre walks in, who just so happens to be friends with the franchisee - he says not to worry, he'll sort it out. The next day I had a different mouse.