Adam Lavin restored South's advantage 10 minutes before the break with a trademark goal - ending a good passing move off with a neat finish.
Chances were few and far between in the second half as South ran out worthy winners.
South boss Jody Marks told JC Sport: "Last season we slipped up against Saints and we were determined not to let the same happen again. It wasn't pretty but am delighted with the three points.
"With two more injuries picked up, we are looking a little depleted as we enter the winter period, but as long as we maintain our fantastic 'true South' spirit, I believe we are still the team to beat to the title."
