2.8 Installing fixed electrical equipment is within the scope of Part P, even if the final connection is by a standard 13A plug and socket, but is notifiable only if it involves work set out in regulation 12(6A)
2.9 Installing prefabricated, modular wiring (for example for kitchen lighting systems) linked by plug and socket connectors is also within the scope of Part P
Quoted from Part P of the Building Regulations 2013. Just to show that there are instances where equipment that is fed from a standard plug and socket need to be given consideration.