At 13-under through 36 holes at the Glendower GC the pair lead from local Jacques Kruyswijk who is at 9-under with a group including veteran Retief Goosen and overnight co-leaders Branden Grace and Chase Koepka a shot further back.
Brett Rumford was the only Australian to make the cut after a second consecutive 1-under 71, Jason Scrivener struggling in his first event of 2018 with a second round 76 that included two double bogeys.
Saddier posted the best round of the day, a 9-under 63 highlighted by a birdie-eagle-birdie finish that gave him a share of the course record.
"The finish was awesome," the Frenchman said of his round. "I started very well, it was quite slow but after I made three birdies in a row on 15, 16 and 17, it was quite good.
"I didn’t know I have a joint course record but it’s quite cool. I’m excited for the weekend but there’s still 36 holes to play and we try to stay focused on the last two rounds."
Paisley, too, is preaching caution at the halfway stage though is excited to be in the mix for the first time.
"I can't wait for the weekend,” he told the European Tour website after his round. “Obviously, I have never been in this position before, so tomorrow, I'm just going to go and play and do my best.
"At the moment it's weird, I feel like I didn't play amazing.”
Paisley added a 7-under 65 to his opening 66 to reach 13-under and has just two dropped shots on his card for the first 36 holes.
Should he go on to win, he would become the third Englishman in four years to hoist the South African Open trophy.
“I certainly hope that I can keep that trend going," he joked.
While Paisley and Saddier are in fine form at the top of the standings it has been a slower start to 2018 for the Australasian contingent with only one of the three in the field making the cut.
For the second straight day Brett Rumford posted four birdies against three bogeys to qualify for the weekend by two shots but both Scrivener and New Zealand’s Josh Geary finished well outside the mark.
Both finished at 6-over for the two days, Geary with scores of 72-78 while Scrivener signed for 74-76.
SIGNATURE HOLES - 15TH AT SYDNEY'S OATLANDS GOLF CLUB:
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