If The Furniture Won't FitThe sensible thing when you order any large piece of furniture is to make sure that it will fit where you need it before you order it. This also means that you should take into account whether it will fit through the door, or whether you'll be able to fit it up the stairs if it's bedroom furniture.
If the worse comes to the worst and you have furniture delivered that just won't go where you need it to, legally it's your fault. Harsh, but fair. Some retailers will take pity on you and let you send the item back, but as far as they are concerned, it's the goodwill of the seller that you're relying on and not a legal obligation. If there really is no way that you can get the item into the house, there may be little choice but for the delivery men to take it back on the van and you'll have to negotiate with the store to see whether they are prepared to offer you a refund. They are more likely to let you have a 'credit note' so that you are obliged to buy more furniture from them - and they don't even have to do that, so you can't insist on more if that's all they will offer you.
The only variation to this is when you order something - having measured up - and it's not the right measurements when it arrives. If the retailer has made a mistake in the description, they are in breach of their contract to you and unless there is another way around it, they have to give you your money back.
As with all big purchases, when it comes to buying furniture, planning is key. Make sure it's what you want, that it will fit where you need it to, and that you tell the seller when you need it, and you shouldn't go far wrong.