Many of those names might as well be the same name given that they are all owned by a handful of groups. The Electrolux group own well over 50 brand names (though not all of them washing machines) Among the more well known ones are AEG, Tricity Bendix, Zanussi. The Candy group own Hoover, Zerowatt and Kelvinator among others. The Indesit Company own Ariston, Indesit, New World, Philco, Hotpoint, Creda, Cannon, GDA, English Electric. Bosch , Neff , Siemens? Same group.
Your John Lewis, was in fact an Electrolux.
The short answer is that you get what you pay for, but what you pay for includes things like service and spare parts availability. Cheaper machines may not be very repairable, for example they may use sealed units for cheaper manufacture and assembly. In fact there is EU legislation coming into force this year that requires greater serviceability and parts availability, but oh whoops Brexit.
Yes, your £1000 Miele may last a long time, but will it last 20 years versus the 5 years you might expect from your £250 Beko? Who knows.