2015 UK Year End Chart1: Mark Ronson ft. Bruno Mars - Uptown Funk (1.76m combined sales in 2015, 2.25m total)
2: OMI - Cheerleader (1.52m combined sales)
3: Hozier - Take Me To Church (1.25m combined sales)
4: Ellie Goulding - Love Me Like You Do (1.19m combined sales)
5: Wiz Khalifa ft. Charlie Puth - See You Again (1.17m combined sales)
6: Adele - Hello (1.12m combined sales)
7: Major Lazer ft. DJ Snake & MØ - Lean On
8: James Bay - Hold Back The River
9: Justin Bieber - What Do You Mean? (988k combined sales)
10: Justin Bieber - Sorry (934k combined sales)
11: Years & Years - King
12: Ed Sheeran - Thinking Out Loud (917k combined sales)
13: Maroon 5 - Sugar
14: Jess Glynne - Hold My Hand (876k combined sales)
15: Skrillex & Diplo ft. Justin Bieber - Where Are U Now (874k combined sales)
16: Jason Derulo - Want To Want Me
17: Lost Frequencies - Are You With Me
18: Rihanna, Kanye West & Paul McCartney - FourFiveSeconds
19: WALK THE MOON - Shut Up And Dance
20: Calvin Harris & Disciples - How Deep Is Your Love
21: The Weeknd - Can't Feel My Face (778k combined sales)
22: Kygo ft. Conrad Sewell - Firestone
23: Fetty Wap - Trap Queen
24: Justin Bieber ft. Ed Sheeran - Love Yourself (719k combined sales)
25: The Weeknd - The Hills
26: The Weeknd - Earned It
27: Little Mix - Black Magic
28: Philip George - Wish You Were Mine
29: Ed Sheeran - Photograph
30: Avicii - The Nights
31: Galantis - Runaway (U & I)
32: Sia - Elastic Heart
33: Ed Sheeran - Bloodstream
34: Charlie Puth ft. Meghan Trainor - Marvin Gaye
35: Olly Murs ft. Demi Lovato - Up
36: Tinie Tempah ft. Jess Glynne - Not Letting Go
37: Years & Years - Shine
38: Chris Brown & Tyga - Ayo
39: Jess Glynne - Don't Be So Hard On Yourself
40: Drake - Hotline Bling
They didn't give the full sales figures, but that should give you a good idea. :)