Nothing of note in the 4th. Div. HQ. diaries.
For the RE Signals you found there is this entry:
10/2/18 Riding school commenced at transport lines for Sappers & Drivers.
This continued until around mid March then nothing about where the men went except about a week later it says that the Signals school was closed & the men went back to their units.
There was a wireless school running along side it but not sure which it refers to.
That only leaves 10 & 11 Bde. diaries.