ManoMano complaint: Refund

I made an order via Mano Mano in October 2022, the items were meant to arrive in 2 weeks but arrived in December 2022. The items arrived which were sofa covers and were poor quality with the thread being out in more than one place. I contacted mano mano for a refund which took 3 weeks to get through to them. The seller then contacted me and gave me an address to send back the items to. I did so and paid £40 out of my own pocket. 1 month later the items are sent back to my address saying the address was invalid. I contacted mano mano who contacted the seller, at first the seller didn’t respond to them and one of the workers at mano mano told me I’d be refunded the price of the items and shipping. Now I’m being told in order for a refund I need to return the items to the seller again. Absolutely shocking and sick to death! It’s been over 6 months!!!