Wowcher complaint: Faulty iMac

Ordered an iMac for my daughters for Christmas, they were excited they could finally do their online homework through the lockdown. Had problems from the get go started off freezing and running slow eventually couldn’t use, kept crashing, sent back to company (IT Trade Services Ltd) at a further cost of £42 to myself as they wouldn’t pay for return, informed Wowcher who did nothing. The company got back to me informing me it needs replacement HDD at a further cost of £95, I’ve refused to pay. They still have my iMac I’m currently going through citizens advice following procedures to go through the Ombudsman. How they can get away with this under the consumer rights act I do not know? Please check the Trader out BEFORE ordering through Wowcher, if I would of done this I would NEVER of ordered the iMac seeing all the complaints about the Trader.