Remember, whatever you buy has to be fit for purpose. If there is something wrong with the screen that means it is effectively unwatchable, then it is not fit for purpose and the shop have no choice.
By selling you the tv they have entered in to a contract with you for the supply of goods, and they can't just make sweeping statements like this.
I would be interested to know if the shop agreed with you regarding the clouding, or whether they have even bothered to inspected the TV you returned.
If the second screen is still faulty, then:
Notify the shop, and ask them what they will do about it. But be polite and courteous in your dealings, even if they are being complete ....
I doubt it would go any further - if there really is a fault with something most places are perfectly good at swapping them out, however if they play you about, tell them you are going to speak to:
- Trading Standards (if people don't actually complain about stores, nobody else will ever find out, and nothing can be done about them).
- Sony UK (do they really want Sony Centres behaving in this way, and what if there is a fault with a batch of panels).
- Now actually make those phone calls, and post back here!