We had this exact same problem, I spent about 4 weeks looking round for TVs (found the one I wanted), waited til Easter weekend and watched prices drop, I was all set on Samsung got into currys anyway I'm not easily persuaded but 4 hours later guy convinces me into a Sony (looked better picture in store) Bought it, got it home, unpacked, was slow as anything and kept loading, picture awful etc etc never had any probs with previous Samsungs even when new, next day took it back (Easter Monday) girl behind counter had a right attitude refused to refund so off they go plugged it in, guy testing then says we have no tv Ariel to test we only have playback chips or whatever they use so I says well it doesn't work, they then say you will have to phone Sony to get a ref number for the fault and they can refund then, so told the now manager that I bought the tele from them and not Sony to which she replies "it's not our tele we don't make them" after about an hour of arguing back and forth I literally hit the roof on bank holiday Monday at the desk, shout girlfriend who has had to walk off cos she's embarrassed, caused a right scene (I'm usually quite polite but the girl was an arrogant sh1t). manager then says ok we will swap so I politely tell her unless shes swapping for a Samsung she can shove her offer and I want a refund, literally another hour passes with all the fuss and they agree to a refund after I go on ranting about trading standards and they're a disgrace and I want the head office details etc etc
Got my refund and I still complained to head office and got a £100 gift card and bought my tv elsewhere just to spite them...had to pay more from John Lewis but it's the principle
Moral of the story, be polite until they refund, if they don't offer refund, kick up a fuss on a busy Saturday with a good audience!