Working out what to do when a product or appliance breaks

Something I own has broken. I need to work out whether it is covered by a warranty or my consumer rights, find the receipt or purchase details, and decide whether repairing or replacing it makes most sense.

• People describe conflicting error-code information, difficulty diagnosing faults, uncertainty about repair costs and fear of paying for a repair only for something else to fail shortly afterwards. (Reddit)
• People frequently discover the problem only when something breaks: the product is potentially covered, but the original receipt or warranty paperwork has disappeared. Citizens Advice says warranty claims will usually require proof of purchase plus information about the warranty and fault. (Reddit)
• People repeatedly ask Reddit whether warranties override statutory rights, what the Consumer Rights Act actually means and how long a retailer remains responsible for a faulty product. (Reddit)