problem with maplin

fersy

i bought some dj speakers and an amp and leads as a package out of maplin a few weeks back. after 3 hours usage one of the speakers blew out. when i took it back they sent it away and i had to wait 3 weeks and now theyve came back and said the speaker was overdriven so they are not prepared to do anything about it.
the thing is the speakers and amp were bought together from them as a match and i never turned the amp over 3 quarters and the mixer levels were not in the red so if the stuff was accurate to the spec they were selling it as i should not have been able to overdrive it.
they are saying they have no way of knowing what i did with the speaker when i took it from them but as far as im concerned by the same token they have no way of proving i operated the equipment irresponsibly as i didnt.
i have phone the office of fair trading and they told me if i wanted a refund (which i did) i needed to prove the item was faulty when i bought it but how am i supposed to do that other than the fact the speaker blew through minimal use but if i just wanted it repaired or replaced then it was up to maplin to prove that i caused the fault. however they will not even repair the fault as they are saying their engineers said the speaker was overdriven thus it had to be my fault.

ive told them not to deliver the items back to me as i wont be accepting them but im a bit lost as to where to go from here as i dont want to sit back and let them get away with this. i operated the gear, i know what happened and no amount of engineers who werent there can tell me otherwise. i faind it amazing tbh that they can get away with washing their hands of this just by blaming me even though they cannot prove conclusively that the equipment was misused.
also i paid by debit card and i heard somewhere i could go down that avenue if i was getting no joy but i dont know

any ideas thanks?