It's not always necessary to open a civil claim. For instance, I had an Apple laptop which developed a major fault 5 years after the purchase date, and well after the warranty had expired Because the laptop was over £2.5K new and it had had previous problems whilst it was under warranty, Apple agreed to carry out the repair free of charge. Furthermore, they agreed that, were it to develop another fault in the next year, it would be replaced with a new model.
These EU consumer protection rules are interpreted with common sense. If you bought a cheap hotpoint fridge/freezer for £120 and is motor packed up after 18 months, a court would probably reasonably conclude that, given the purchase price, you probably had 'fair use' out of it and had no case. However, if you'd bought a top of the range Miele one for £1700, it would reasonably be expected to last longer than 18 months. But as Louise66 says, if the retailer (with whom you have the contract, not the manufacturer) disagrees with your refund/repair claim, the only way to have it assessed is to start a civil claim, which can be both lengthy and costly with no guarantee of success.