The combat pistol shooting technique taught by the British Army in WW2 was known as "point shooting" or "reflex shooting"
Much as I hate to link to a Wiki, it describes it well:
http://en.wikipedia.org/wiki/Point_shooting
Note the US army's two handed variation.
The choice for one handed firing was purely an artistic one - it looked cooler and more desperate and more in-keeping with the historical nature of the firearm.
I have to confess I have only ever shot pistols two handed,hell, I couldn't even keep the magum still with two hands let alone one. However I imagine there's a vast difference between target shooting and shooting in a combat environment