Excellen thread.
Sigur Ros - You probably know these guys since they've been on adverts and sports show background music for years but you mention their name and no one has a clue who they are.
Hoppipolla
Saeglopur
Milano
Explosions in the Sky
Breathtaking instrumental post rock.
Your Hand in Mine
First Breath After Coma
The Only Moment We Are Alone
Those 2 are maybe a bit left field for what your average JTer is likely to be into so I'll throw in some Longview but they're definitely worth a listen. Great chill out / reading music.
Longview
Great UK Indie band that really should have been absolutely massive.
Nowhere
Will You Wait Here?
Can't Explain