Gotye moves up to two with his international hit 'Somebody That I Used To Know', while The Wanted advance a place to three with 'Glad You Came'.
One Direction shoot up to number four on the chart with 'What Makes You Beautiful', Justin Bieber slips to five with 'Boyfriend' and Nicki Minaj stays put at six with 'Starships'.
Carly Rae Jepsen is at ten with 'Call Me Maybe', Drake and Rihanna trail at 11 with 'Take Care' and Calvin Harris moves up to 13 with 'Feel So Close'.
Further down the chart, Adele's 'Rumour Has It' is up to 23, Jennifer Lopez's latest single 'Dance Again' debuts at 27 and Usher is at 30 with 'Climax'.
Elsewhere, Rihanna and Chris Brown's 'Birthday Cake' is at 32, Kanye West's 'Mercy' premieres at number 38 and Ellie Goulding is at 60 with 'Lights'.
The Top 10 singles in full (click where possible for our reviews):
1. (1) fun. ft. Janelle Monáe: 'We Are Young'
2. (3) Gotye ft. Kimbra: 'Somebody That I Used To Know'
3. (4) The Wanted: 'Glad You Came'
4. (9) One Direction: 'What Makes You Beautiful'
5. (2) Justin Bieber: 'Boyfriend'
6. (6) Nicki Minaj: 'Starships'
7. (12) Flo Rida ft. Sia: 'Wild Ones'
8. (5) Kelly Clarkson: 'Stronger (What Doesn't Kill You)'
9. (8) Katy Perry: 'Part of Me'
10. (10) Carly Rae Jepsen: 'Call Me Maybe'
Watch fun.'s 'We Are Young' music video below: