UK design rights do not cover the 2D aspects of a design. For instance the surface decoration of an object is not protected by UK design right protection. You would need to register the design.
Designs that are commonplace or ordinary do not qualify for protection either.
Design features enabling one product to be functionally fitted or aesthetically matched to another get no protection.
These exceptions are known as the ‘must-fit’ and ‘must-match’ exceptions and are there so that competing designs for spare parts cannot be kept out of the market.
Competitors cannot be stopped from copying any features of a protected design that enables their own design to be connected to or matched with existing equipment designed by someone else. However, competitors will infringe design right if they copy features of a protected design where there is no need to do so.