I have seem many times where letters are used. To say fused connection unit (FCU) then continue after to call it a FCU is OK as people then know what your talking about. The RCCB, RCD, GFCI, ALCI, ELCB-c and ELCB-v must really confuse the DIY guy and to then add even more sets of letters just adds to it. QSL
I have many times said with an international Q code why do people want to add yet more sets of letters LOL.
The 10 code is of course not permitted but Q code is!
The whole forum is full of CU, FCU, RCD, RCBO and the list goes on.
When using Morse code I can understand using QTH instead of "What is your position in position" but really there is no real need with the written word. Even the international Q-Code has changed through the years I often use QRM to ask if the XYL is nagging. But son's wife is slowly learning Q-code so that will have to stop.
As to where to daisy chain from using the switch box means longer cables and no permanent line to charge the batteries on any emergency lamps. There are times when one has to do something non standard but unless there is no option the idea of having a supply non switched at the ceiling rose makes sense.
What we need is instead of a block of Smilies to left an array of short forms so we can just click on CU and it will auto type Consumer Unit.