It's quite clear - if you sell something then the usual requirements in the acts apply. If it goes wrong you are expected to provide a solution - which is usually a refund, a repair or replacement. The new act is somewhat vague, but I think better for the seller - as the old one was peppered with the word "reasonable" which nobody really agreed on.
It now talks about the contract - so if you sell an item and you describe it in the ad, or blurb on the product in the shop, you have made a contract, and they have an expectation.
Mail order now seems to have become settled on the 14 day refund for no reason at all, but you still do not need to refund in a shop just because they change their mind. If the product dies, or fails - then it no longer does what the contract said it would - so if it fails before 6 months from date of sale, you have to do something - to meet the contract terms. A replacement is fine, a refund if they really stand their ground, but the refund can be for a lower amount to balance the use they've had.
In short - up until six months has passed, you have to do something - but have wiggle room. After six months you can breath. The expectation is that many firms will continue to use the words 12 months guarantee, and this is covered by the new act as a separate thing - if you give the guarantee, you must honour it.