@PoorOldSpike
Yes, there is a way for a user to stop Steam from automatically updating your games.
1) Bring up Steam
2) Under 'Library' go to 'All Games'
3) Right-click on whichever game you desire
4) Left-click 'Properties' and the 'GameName - Properties' window will pop up
5) Left-click on the 'Updates' tab
6) Set the 'Automatic Updates' and 'Background downloads' properties to whatever you desire via their respective drop-down menus
Hope this helps! :o
- S-G-M