There are two ways to play the Verse/Intro & Pre-chorus.
The Open Position (aka, only using frets 1-4 and open)
is easier, but the slide method is the "real" way.

*****************************************************
*Open Position                                      *          
*Intro/Verse                                        *
*G|-----------------------|-----------------------| *
*D|---0-4---------0-------|---0-------------------| *
*A|-2---------------3-2-0-|-2---4---------3-2-0---| *
*E|-------2-3-2-3---------|-------2-3-2-3-------3-| *
*                                                   *
*Pre-chorus                                         *
*G|-----------------------|                         *
*D|---0-4-----------------|                         *
*A|-2-------------2-0-0-0-|                         *
*E|-------2-3-2-3---------|                         *
*****************************************************

Slide Method
Intro/Verse
G|-------------------------|-----------------------| x4
D|------4------------------|-----------------------|
A|----5--------------------|---5-3-----------------|
E|3/7-----2-3-2-3/10-8-7-5-|-7-----2-3-2-3/8-7-5-3-|

Pre-chorus
G|-----------------------|
D|-----4-----------------|
A|---5-------------------|
E|-7-----2-3-2-3-7-5-5-5-|

Chorus         
G|-----------------------|--------------------|
D|-----5h7p5-------------|--------------------|
A|---0-------7-5-----3-5-|77-----4-5-0-5------|
E|-0-------------3-5-----|---557---------3-0-3|

G|-----------------------|--------------------|
D|-----5h7p5-------------|---------------5-5-5|
A|---0-------7-5-----3-5-|77-----4-5-0-5------|
E|-0-------------3-5-----|---557--------------|

G|-----------------------|---------------------| <-Tricky double slide
D|-----------------------|-7-7-7-77-6-6-6--55/2|   back into the verse.
A|-----------------------|---------------------|   5/2 on the D-string
E|-5-5-5-55-4-4-4--3-33--|---------------------|   to 3/7 on the E-
            |-3-|                   |-3-|          string.


Verse x2
Pre-chorus
Chorus
Verse x3
Pre-chorus

Extended Chorus
G|-----------------------|--------------------|
D|-----5h7p5-------------|--------------------|
A|---0-------7-5-----3-5-|77-----4-5-0-5------|
E|-0-------------3-5-----|---557---------3-0-3|

G|-----------------------|--------------------|
D|-----5h7p5-------------|---------------5-5-5|
A|---0-------7-5-----3-5-|77-----4-5-0-5------|
E|-0-------------3-5-----|---557--------------|

G|-----------------|----------------------| x2
D|----7-7------555-|----7-7---------------|
A|-77--7-7-505-----|-77--7-7-505-----3-5--|
E|-----------------|-------------3-5------|

G|-----------------------|---------------------| x2
D|-----------------------|-7-7-7-77-6-6-6--55/2|
A|-----------------------|---------------------|
E|-5-5-5-55-4-4-4--3-33--|---------------------|
            |-3-|                   |-3-|       

End note (let ring)
G|----|
D|----|
A|----|
E|-/5-|