3" Mortar Emplacements benefit to some extent, similarly to the 25 Pounder Gun Howitzers.
Other units are also augmented by the Royal Artillery Support tree. With this tech tree, the 25 Pounder Gun Howitzer becomes one of the most powerful units on the battlefield, capable of raining destruction on pretty much any enemy target, blocking enemy advance routes with constant bombardment, and shut down the enemy's own field artillery. On top of this, a British Commander receiving Royal Artillery Support can both increase the potential of his existing artillery, as well as implement new types of artillery that are not otherwise available. They offer their troops the aid of powerful artillery units, including the fearsome 25 Pounder Gun Howitzer.
The British base much of their World War II operations on lessons learned from World War I.