The track, which slipped to three last week after first reaching pole position a fortnight ago, beat Emeli Sandé's 'Next To Me' into second place with a lead of 25,000 copies.
Last week's victor 'Hot Right Now' from DJ Fresh and Rita Ora is in third place, while 'Wild Ones' by Flo Rida and 'Titanium' by David Guetta - both of which feature Sia - swap places at four and five respectively.
Elswehere, Nicki Minaj scores her highest ever UK chart entry with 'Starships', up nine to seven, which is followed by her David Guetta team-up 'Turn Me On', at eight from last Sunday's 11. Also celebrating are Gym Class Heroes, who grab the week's highest new entry at nine with their Neon Hitch collaboration 'Ass Back Home'
Outside the Top 10, Ed Sheeran is up six to 11 with 'Drunk', Alyssa Reid's 'Alone Again' drops from seven to 12 and Rizzle Kicks slip three to 15 with 'Mama Do The Hump'.
LMFAO boost a hefty 19 places up the rankings to 16 with 'Sexy & I Know It' and Sheeran makes another appearance at 17, bounding from last week's 37 with 'Lego House' following his performance of the track at Tuesday's (February 21) Brit Awards. Its sales have increased by more than 100% since the ceremony.
Former number one 'Twilight' by Cover Drive crashes nine to 19 in its fifth week of release, as Rihanna and Adele climb back up the numbers in the wake of their own Brits appearances.
The Bajan star's 'We Found Love' is up 12 to 22 after a 52% sales boost, while Adele's 'Rolling In The Deep' is up 11 to 28 and her track 'Someone Like You', performed at last year's Brits, re-enters at 32.
Source: Official Charts Company
> This week's albums chart