Owain wrote:

Such a unit (also incorporating a cooker control switch) was marketed as
a "Kitchen Control Unit" for new post-war housing in 1947, but I don't
see a reference to "consumer unit" as such.

There was an article in a recent /Wiring Matters/ [1] on the origins of
the BS 1363 and ring circuits, etc. This focusses on a report [2]
published in 1944 which established much of the basis for wiring
practices which are still with us sixty years later. The article refers
to the report "mak[ing] proposals for single-pole fusing, a novel
compact design of consumer control unit, the cooker control unit [etc.,
etc.]"

That would put the first use of the term "consumer (control) unit" at
somewhere between 1942 (when the work started) and 1944.

[1]http://www.iee.org/Publish/WireRegs/WiringMatters/Documents/Issue18/2006_18_spring_wiring_matters_bs_1363_plug_and_soc ket.pdf
[2] Post-war building study no. 11 - Electrical installations.

--
Andy