All three are starting their second match of the tournament. Robson started against Italy while Britton and Mills got the nod against Ireland.
Chris Walker is recalled to the starting line-up and again captains the side, while Sam Hill, Robson, Luke Cowan-Dickie, Sam Twomey and Billy Vunipola also come into the starting fifteen.
A win guarantees England a spot in the semi finals, but defeat would not necessarily rule out a last four place.
Head Coach Rob Hunter says that the squad is looking forward to what promises to be an entertaining match:
"We're very excited about the game," he said. "When the Pools were announced we knew that this one was going to be a fantastic match-up. Playing the Baby Boks in their own back yard will be a memorable experience and I'm sure that there will be a great atmosphere.
"As a squad we're feeling pretty fresh, we had a tough game against Ireland and we've made a few changes from that starting team but we're very focused on the task in hand and can't wait to get out there."
"Of course we're going for the win, it's the best way to ensure we make it out of the group, we don't want to leave it to math. Last year's game against South Africa was incredibly physical, it was one of the games of the tournament, and we're expecting exactly the same."
England Under 20 starting XV:
15 Tommy Bell (London Wasps)
14 Marland Yarde (London Irish)
13 Sam Hill (Exeter Chiefs)
12 Ryan Mills (Gloucester Rugby)
11 Charlie Walker (Harlequins)
10 Tom Heathcote (Bath Rugby)
9 Dan Robson (Gloucester Rugby)
1 Luke Cowan-Dickie (Exeter Chiefs)
2 Koree Britton (Gloucester Rugby)
3 Kyle Sinckler (Harlequins)
4 Sam Twomey (Harlequins)
5 Dominic Barrow (Leeds Carnegie)
6 Billy Vunipola (London Wasps)
7 Chris Walker (Leeds Carnegie) (C)
8 Jack Clifford (Harlequins)
16 Nathan Morris (London Wasps)
17 Alec Hepburn (London Wasps)
18 Ross Harrison (Sale Sharks)
19 George Merrick (Harlequins)
20 Ben Nutley (Northampton)
21 Ben Spencer (Saracens)
22 Josh Bassett (Bedford Blues)
23 Ben Ransom (Saracens)