HiWhat do I do about a seller declining a return without them resolving the issue?

[colivia08]

I received a clear glass dining table in a very damaged box with parts of the table sticking out and footprints all over the box. The fault with the table was with one of the parts sticking out of the box, this now has affected the extending part of the table. I contacted the seller to advise and also sent photos. They have stalled over a few weeks with various questions until they decided to deliver a new table and collect the faulty one. A date and time was arranged, my husband took the day off work and no one turned up !!! After more messages backwards and forwards they arranged another date. Two days before the arranged date they messaged to say the item was no longer in stock  but I could have a black one. I advised them I didnt want this and told them I would accept a discount  and try and get the table fixed. They offered me £20 ! I told them I would return the item for a full refund. They have declined the return request and not resolved the issue. What do I do now?