Keith, I had a little google (actually a Duck Duck Go) and found this reference - perhaps a Nuffield set was simply one donated by the Nuffield Trust?
http://www.nuffieldtrust.org/fifty.htm
' In war-time, one of the first things the Trust did was to distribute thousands of radio sets to the British Expeditionary Force. Later thousands more were sent to ships at sea and isolated A.A. sites and barrage balloon units at home'.