The track leads the tally for a third week, fending off competition from Birdy's 'Skinny Love', which jumps from four to two.
Meanwhile, the rest of the top ten remains static, with the exception of Birdy's 'People Help The People', which lifts 13 to ten.
Outside the top ten, David Guetta and Sia's 'She Wolf (Falling To Pieces)' lands at 11, Chiddy Bang's 'Mind Your Manners' leaps 17 to 14, and James Morrison's 'I Won't Let You Go' vaults 38 to 18.
Ne-Yo's 'Let Me Love You' charges 46 to 22, Rita Ora ft Tinie Tempah's 'R.I.P' starts 29, and Marina and the Diamonds jumps 39 to 36 with 'Primadonna'.
Outside the top 40, NIcki Minaj's 'Starships' re-enters at 46, Duffy's 'Mercy' is at 47, and Ora's 'How We Do (Party)' bows at 50.
The Top 10 singles in full (click where possible for our reviews):
1. (1) Guy Sebastian ft. Lupe Fiasco: 'Battle Scars'
2. (4) Birdy: 'Skinny Love'
3. (2) Justice Crew: 'Boom Boom'
4. (3) Taylor Swift: 'We Are Never Ever Getting Back Together'
5. (5) Maroon 5: 'One More Night'
6. (6) Owl City ft. Carly Rae Jepsen: 'Good Time'
7. (7) The Script ft. will.i.am: 'Hall Of Fame'
8. (8) Far*East Movement ft. Cover Drive: 'Turn Up The Love'
9. (9) fun. 'Some Nights'
10. (13) Birdy: 'People Help The People'
Listen to Guy Sebastian's 'Battle Scars' below: