Broken Bed

I bought a bed from Sainsbury's in January which was delivered in February. Here we are, seven months later, the wood on part of the frame has started to split. Sainsbury's have said the manufacturer will only pick it up if it's dismantled and in it's original packaging(!), however, if I tell them what bits have split, they will send replacements parts.

I don't want replacement parts, I want either a new bed or a refund, does anyone know where I stand? Sainsbury's have gone on automatic pilot and keep saying the same thing over and over again.