What constitutes infringement of a UK registered design?
There is no question of knowledge or intention when it comes to registered design infringment (although this does have an affect on the available remedies). Simply the fact that the design is registered gives notice to everyone, regardless of their actual knowledge of the design or of their infringement of the design.
A registered design gives the proprietor the exclusive right to use the design and “any design which does not produce on the informed user a different overall impression” (s7(1)). One of the points of confusion with registered design infringement was dealt with in the case of Rowlawn Ltd v Turfmech Machinery Ltd  EWHC 989 (Pat), the issue was that of distinguishing between an overall design concept and the particular features of a design that are protected by registration. In the Rowlawn case the defendant followed the broad concept of the design, however this is not what the registered design itself protected and as the finer details of the machine there was no copying and thus no infringement.
Use of a design is defined in s 7(2) as “making, offering, putting on the market, importing, exporting or using of a product in which the design is incoporated or to which it is applied”. Infringement itself is simply doing anything that is the exclusive right of the proprietor withough its consent (s 7A). As always there are exceptions which include (s 7A(2):
1) an act which is done privately and for purposes which are not commercial
2) an act which is done for experimental purposes
3) ac act of reproduction for teaching purposes
There are of course more but the above tend to be the most prevalent. It is also important to be aware that there cannot be an infringement of a design before the date on which it is registered.