Oh wow, I'm glad to have found this thread! I'm such a huge fan of the Sugababes and had always been interested in their unreleased material. I started doing research about it and found a lot of leftover tracks from One Touch registered on APRA AMCOS a year ago. Here's a list of what I was able to find that hasn't leaked yet
One Touch
Boys Will Be Boys
Date (also known as "Do You Want a Date With Me")
Heaven
My Life
New Generation (also know as "New Generation (Children of The Future)")
No Doubt
Second Best
Stop, Look, Listen
Groove Is Going On (I did find this registered with Siobhan's name on there but idk if that was an error or not)
Angels With Dirty Faces
Don't Wake Up (Miranda Cooper of Xenomania mentioned this in a 2015 podcast interview of Sodajerker, this may have been retooled as "Don't Wait Up" which was released in 2006 by girl group Frank)
Great and Secret Show (Was mentioned by a user on Popjustice who allegedly found it on a reel of remixes and and productions by Agent X)
I Wanna Dance With Numbers
Snake Around My Heart (Demo by Wayne Hector leaked online)
The Only One
The Word (Mentioned in a 2002 press release for "Angels" but I believe this could be a Heidi mix for All Around The World)
Three
Again and Again
Bodyrockin'
First Love
Let's Go Crazy
Liberation
Money Money
Whisper (A user on an old Sugababes forum said Heidi performed it on the promotional tour for Three)
Xpress
Taller In More Ways
Dead Man Walking
Have You Ever
Heatwave (Mentioned in a December 2005 MTV Trax article as a B-side to Red Dress prior to Mutya's departure)
Jason's Eyes
Lustful Dancefloor (Mentioned in a December 2005 MTV Trax article as a B-Side to Red Dress)
Never Gonna Dance Again (Mutya Mix)
Schitzophernia
Strung Out (It's been said to have been recorded by 2.0 for Taller and re-recorded with Amelle for the re-release)
Time Is a Healer
Change
Black Glasses (Rumored B-side for the Change single)
Keep Sane (Rumor)
Pussycats (Rumor)
Time (Rumored B-side for the Change single)
Underwater (Rumored B-side for the Denial single)
Unknown track produced by JC Chazez (Mentioned in The Daily Star in February of 2007)
Catfights & Spotlights
Everybody Nose [N.E.R.D. Cover] (Mentioned in The Guardian in October of 2008)
4.0 2011 sessions
Hard (The proposed 2nd single after Freedom)
Tetris
Split Personality
Wrong Again