sammilou --- You have no problems here as the suite was only just delivered and the damage was present on delivery possibly witnessed by family, the fact the driver did not pass the information on is not your fault at all.
Simply tell them you want to reject it under, "the sale of goods act" as unfit for it's purpose and demand as above, either a full refund or at your choice a replacement delivered as per the timescale that they will put in writing.
Those are your legal rights, if they refuse they are breaking the law.
PS -- Do not let them fob you off, or accept any offer to repair. This could lead to long delays with the damage never actually getting repaired, demand a refund or a replacement subject to your agreed re-delivery period put in writing only.