Refusal to exchange a collapsed bed

Very Disappointing service received from Dial a bed, Hemingways. I purchased a bed from them (40Winks) and within a year (While Still under guarantee, the bed collapsed in a certain section. I reported the matter, requesting a new bed. I submitted the requested photos and waited, and waited. Now they are saying that they refuse to replace or restore the bed because they see a "Mark" on the mattress. I requested to have the relevant representative to come out and inspect the bed for themselves, as there is not a mark on the mattress, to which they say, "that isn't possible" They also refuse to give me the contact information for Forty Winks, and say they will pass on the message. This is unacceptable service and a direct infringement of the CPA. I will definitely not be leaving this here.