Ok, I'm pretty sure it's 100% correct. Pick the chords during the verses and strum them
during the chorus. it sounds much better with 2 guitars...

Chords:

G |---7---|
  |----8--|
  |-----7-|
  |-------|
  |-------|
  |-------|

--> chorus : G (779787) and/or G (320033)

D |---5---|
  |----7--|
  |-----7-|
  |-------|
  |-------|
  |-------|

--> chorus : D (555775) and/or D(000232)

C/B |---3---|
    |----5--|
    |-----4-|
    |-------|
    |-------|
    |-------|

--> chorus : C/B (005453)

C |---3---|
  |----5--|
  |-----5-|
  |-------|
  |-------|
  |-------|

--> chorus : C (335553) and/or C (032010)


Verse:

G               D
I'm thinking of you
C/B     C
In my sleep
G                D
They're not good thoughts
C/B               C
The worst kind of sad
G             D
I've noticed things
C/B         C
Cannot be repaired
G           D
When I wake up
C/B           C
I'll be in despair


Cos I know I've got to say
I know I've got to say

Chorus:

G     D    C/B     C
Goodbye    baby goodbye
Goodbye    baby goodbye
G              D     C/B     C
You're my sweetheart goodbye
You're my sweetest   goodbye

--> continue the same way through the whole song...