You don't need the original box to receive warranty service.
Make a Genius Bar appointment at the closest Apple retail store. Or the closest authorized Apple Service provider. In some countries, you can also take care of warranty service online.
World-wide Apple Support -
Contact Apple for support and service – Apple Support (UK)
M1 Mac mini, macOS 13.5; Watch, series 7 GPS/cellular, watchOS 9.6; iPad Pro 2nd Gen, iPadOS 16.6; iPhone 12 Pro, iOS 16.6; TV 4th Gen, tvOS 16.6; HomePods, audioOS 16.5 and Airport Express w/ Airplay 2