"it still resulted in many people volunteering on the false impression that they would not be there long."

The over or home by Christmas line was NOT spread by Government.

Looking at it logically:

1: Between August 1914 and December 1914 1.2 million young men volunteered to join the Army

2: The British Army of the day was at full strength including reserves was roughly 440,000 men

3: For there to be any credibility in the over by Christmas how were the 1.2 million going to be trained? Who was going to train them? Where were they going to be trained? Impossible in that time frame.

4: For there to be any credibility in the over by Christmas how were the 1.2 million going to be clothed and armed? Impossible in that time frame.

5: British Army roughly 440,000 with an additional 1.2 million waiting in the wings (Harry Patch conscripted in October 1916 was not deployed to France until June 1917 - by the time Harry was conscripted the training barracks, the equipment available the supply train was all in place - it wasn't in 1914) was up against a fully mobilised German Army of 4.5 million. Now I know the British might have had a slighly over-inflated opinion of their capabilities but I do not think that that would stretch to them defeating the largest and best trained army in the world inside 5 months whilst being outnumbered 10:1 - Simply impossible that it could ever be over by Christmas.