I was more curious than anything, so I whipped up this list. Bold are headline acts, the rest are supports.
New news post because no-one goes through peoples old news posts.
2005
Franz Ferdinand
The Editors
The Rakes
2006
We Are Scientists
The Cinematics
Foreign Born
The Rakes
Sean Na Na
The Klaxons [Before they were famous, I thought they were shit]
The Zutons
The Rumble Strips
Red Hot Chili Peppers
!!! [Chk Chk Chk]
Ben & Jerry's Sundae On The Common [festival]
Jose Gonzales
The Wonderstuff
Captain
Vincent Vincent & The Villains
Carling Weekend Reading 2006 [festival]
Friday
Franz Ferdinand
Kaiser Chiefs
Yeah Yeah Yeahs
Mystery Jets
The Subways
Gogol Bordello
Saturday
Muse
Arctic Monkeys
The Streets
Dirty Pretty Things
The Futureheads
The Cribs
Wolfmother
Sunday
Maximo Park
The Rakes
The Kooks
Boy Kill Boy
Broken Social Scene
Goldie Lookin Chain
Hope Of The State
The Dresden Dolls
¡Forward Russia!
Tapes 'n' Tapes
Metric
The Marshalls
The Automatic
The Alterkicks
We Are Scientists
Hot Club De Paris
Au Revoir Simone
XFM Winter Wonderland [festival]
Kasabian
Tenacious D
The Kooks
The Feeling
The Automatic
Boy Kill Boy
Just Jack
Tenacious D
2007
Muse
The Streets
Dirty Pretty Things
Rodrigo Y Gabriella
Carling Reading Weekend 2007 [festival]
Friday
Ash
Kings Of Leon
Interpol
Get Cape. Wear Cape. Fly.
The Enemy
Gogol Bordello
The Long Blondes
Little Man Tate
The Pipettes
Saturday
Red Hot Chili Peppers
Arcade Fire
Bloc Party
The Pigeon Detectives
The Young Knives
Good Shoes
The Noisettes
Sunday
Klaxons
LCD Soundsystem
CSS
Jamie T
Devendra Bernhart
The Cold War Kids
The Maccabees
The Sunshine Underground
Pull Tiger Tail
Late Of The Pier
The Maccabees
Derek Meins
Kid Harpoon
Talk Taxis
Bloc Party [with Exmoor Choir]
Maps
We Are Scientists
The Cinematics
Kid Harpoon
Good Shoes
Operator Please
Ida Maria
Bill Bailey
Kaiser Chiefs
The Pigeon Detectives
Joe Lean & The Jing Jang Jong
Art Brut
A-Human
2008
NME Big Gig 2008
Manic Street Preachers
Bloc Party
Kaiser Chiefs
Klaxons
The Cribs
Reel Big Fish
Streetlight Manifesto
Sonic Boom Six
Radiohead
V Festival
Sunday
Muse
Stereophonics
The Kooks
Maximo Park
Reading Festival
Friday
Rage Against The Machine
Dan Le Sac vs Scroobius Pip
Does It Offend You, Yeah?
Queens of the Stone Age
The Fratellis
Get Cape. Wear Cape. Fly
Anti-Flag
Saturday
The Killers
Bloc Party
The Raconteurs
Editors
We Are Scientists
Mystery Jets
We Are Scientists acoustic set
Bombay Bicycle Club
Sunday
Metallica
Tenacious D
Feeder
Mindless Self Indulgence
Hadouken
Cajun Dance Party
Mystery Jets
Golden Silvers
The Futureheads
Johnny Foreigner
The Futureheads
TV on the Radio
Bloc Party
Tommy Sparks
Wet Paint
---FUTURE---
Franz Ferdinand
Bloc Party
Foals
Maximo Park
AxeWarrior
There are some bands here I'm glad to say I've seen that you haven't. Pearl Jam, GWAR, Motley Crue, Buckcherry, and Posion (5 times) to name a few