Basically in the United Kingdom you will have a standard 12 month warranty, but if the product is supposed to last considerably longer than one year, you may be able to return a product for a refund or replacement for up to 6 years, if you can prove it was defected. This will apply to TV, PC and mobile phones, et cetera.
A guarantee is something the manufacturer or seller may choose to give you. The warranty will not give you anything more than you already are entitled to by law - either in time or scope. For example, the seller may choose to give you the right to return the item, even if it is you who has caused the fault.
If you discover a fault in the first 12 months after purchase, the seller has a responsibility to replace the item/s. If the seller can prove that the fault is due to something you have done, you must pay for the repairs yourself.
The seller always has a duty to inspect the goods after you have returned them. After a year, you can no longer assume that the fault was caused by a weakness in the goods. Further investigation may be needed to determine if the goods were faulty from the start. Remember that the seller can only charge for repair or examination if it is agreed in advance and the product fault is your responsibility.
When an item is sold as used, it is often "sold as is". It limits your rights, but you may still have a right to a warranty if: