RICHMOND UPON THAMES LBC v ARIYO ( (2024) EWCA Civ 960 is concerned with the general principle of planning law that changes of use are generally judged by reference to the “ planning unit “.
The planning unit , at least in general terms, is the whole of an area in single occupation used for a main purpose to which other purposes are ancillary. The concept of an ancillary use is also a well-established part of planning law; and where a change of use is permitted it will generally extend to land used as ancillary to the changed use, if part of the same planning unit.