314.4 sets out the requirement to connect each final circuit to a separate way in a distribution board. A split board provides that.

314.1 indent (i) sets out two of the reasons why installations should be divided into circuits, one of which is to minimize inconvenience in the event of a fault. The notion of "inconvenience" is a subjective one. It could be contended that the only person able to make that call would be the user of the installation. Without the input of the user, a designer could only speculate on what would cause "inconvenience". However, if it is established that inconvenience could be caused by the tripping of more than one circuit because of a fault, then the next step is ensure that the "inconvenience" is "minimized".

To "minimize" something is to reduce it to the lowest possible degree. If the user or designer considers multiple circuit disconnection in the event of fault would be an inconvenience then the designer must "minimize" that possibility.  A split board arrangement would not provide that and would therefore not meet 314.1 indent (i).

There is nothing in 314.1 about cost. It is a "shall" regulation.

Any one wishing to explore the meaning of "inconvenience" might like to ask folk in Manchester (today around 3pm) if it would be "inconvenient" if a fault in their kettle also disconnected their TV!

To "minimize" something is to reduce it to the lowest possible degree.

But not necessarily without regard to all other factors - e.g.. acceptable cost. That's why it's minimised rather than eliminated,

  - Andy.

To "minimize" something is to reduce it to the lowest possible degree.

But not necessarily without regard to all other factors - e.g.. acceptable cost. That's why it's minimised rather than eliminated,

  - Andy.