Since the product involved is a couch, you might be advised to use the furniture ombudsman to resolve the dispute.
However I would advise you avoid them like the plaque – I was involved in a dispute that I placed before them, which was found in the retailers favour (despite trading standards advising me that the retailer was in the wrong).
I then investigated the furniture ombudsman to find that it is an organisation funded by the retailers (no conflict of interest there, then).
Unfortunately since I had placed the matter before the furniture ombudsman for a ruling, the financial ombudsman refused to investigate the matter.
Although banks and other financial institutions fund the financial ombudsman service – it is mandatory that they pay into the scheme – whereas the furniture ombudsman has to attract members to pay their fees, in order to stay in business.
So you have been warned – avoid the furniture ombudsman at all costs.