where did they play?
The Royal Field Artillery were supposed to have played against "Prussians and Hanovers" near Ypres.
Christmas truce
the Royal Field Artillery against "Prussians and Hanovers" near Ypres and the Lancashire Fusiliers near Le Touquet, with the detail of a bully beef ration tin as the "ball". 
did they play football on christmas day in ww1 Yes, in 1914 as a part of the Christmas truce between German and British troops.
wiki:19100563
Christmas truce [SEP] Football matches
One recent writer has identified 29 reports of football, though does not give substantive details. Colonel J. E. B. Seely recorded in his diary for Christmas Day that he had been "Invited to football match between Saxons and English on New Year's Day", but this does not appear to have taken place.