Replacing an appliance would be fine without testing or notification. Ultimately it's no different to unplugging the f*cker.

Part P is most concerned with notification / building regs, but also imposes a requirement for ALL work (whether notifiy-able or not) to be tested in accordance with 17th ed and for the person testing to be QUALIFIED (n.b. NOT 'competant') in such testing.

So although adding a spur to an existing circuit is not notifiable, if you're fitting it in the course of your profession, it must be tested and certified.

Chris