My go at a Sean-style thread. Rock, as you'll see, is a very elastic definition.

Singles:
1 COLDPLAY - PARADISE 410,000
2 GOO GOO DOLLS - IRIS 264,000
3 BIRDY - SKINNY LOVE 259,000
4 COLDPLAY - EVERY TEARDROP IS A WATERFALL 247,000
5 NOAH & THE WHALE - L.I.F.E.G.O.E.S.O.N. 242,000
6 JAMES MORRISON - I WON'T LET YOU GO 228,000
7 FOSTER THE PEOPLE - PUMPED UP KICKS 225,000
8 SNOW PATROL - CHASING CARS 128,000
9 FLORENCE & THE MACHINE - SHAKE IT OUT 127,000
10 THE CALLING - WHEREVER YOU WILL GO 125,000
11 COLDPLAY - FIX YOU 124,000
12 NOEL GALLAGHER'S HIGH FLYING BIRDS - AKA WHAT A LIFE 115,000
13 ELBOW - ONE DAY LIKE THIS 104,000
14 NIRVANA - SMELLS LIKE TEEN SPIRIT 102,960
15 SNOW PATROL - CALLED OUT IN THE DARK 102,950
16 DAMIEN RICE - CANNONBALL 99,000
17 EVANESCENCE - BRING ME TO LIFE 98,000
18 COLDPLAY - VIVA LA VIDA 96,000
19 KINGS OF LEON - SEX ON FIRE 90,000
20 ARCTIC MONKEYS - DON'T SIT DOWN 'CAUSE I'VE MOVED YOUR 81,000

Albums:
1 COLDPLAY - MYLO XYLOTO 908,000
NOEL GALLAGHER'S HIGH FLYING BIRDS - NOEL GALLAGHER'S HIGH FLYING BIRDS 492,000
3 FLORENCE & THE MACHINE - CEREMONIALS 384,000
4 FOO FIGHTERS - WASTING LIGHT 380,000
5 MUMFORD & SONS - SIGH NO MORE 373,000
6 ELBOW - BUILD A ROCKET BOYS 327,000
7 KASABIAN - VELOCIRAPTOR 279,000
8 SNOW PATROL - FALLEN EMPIRES 269,000
9 NOAH & THE WHALE - LAST NIGHT ON EARTH 261,000
10 ARCTIC MONKEYS - SUCK IT AND SEE 223,000
11 THE VACCINES - WHAT DID YOU EXPECT FROM THE VACCINES 214,000
12 FLORENCE & THE MACHINE - LUNGS 198,000
13 RED HOT CHILI PEPPERS - I'M WITH YOU 178,000
14 FOO FIGHTERS - GREATEST HITS 172,000
15 BEADY EYE - DIFFERENT GEAR STILL SPEEDING 165,900
16 KINGS OF LEON - COME AROUND SUNDOWN 165,600
17 TWO DOOR CINEMA CLUB - TOURIST HISTORY 156,000
18 FLEET FOXES - HELPLESSNESS BLUES 134,000
19 PJ HARVEY - LET ENGLAND SHAKE 121,000
20 KINGS OF LEON - ONLY BY THE NIGHT 120,000