G
D
Em (3 3 0 2 2 0)
C (3 3 0 2 3 0)

Put a Capo on the 2nd fret

Song starts with picking, I think you can play around to figure it out. I think 
it's something like this

e - - - - -3 -- - - - -| 
b - - - - - -3 - - - - |
G - - - - - - 0 - - - -|           --> and repeat this...this is basically it.
D - - - 0 - - - - - - -|
A - - - - - - - - - - -| 
E - - 3 - - - - 3 - - -| 

G
Here we come a-wassailing among the leaves so green,
Here we come a wandering so fairly to be seen

                                                 (walk down on A-string 3-2-0 during these chords)
Em              D              C - Em      D  
Here we come a-wandering so fairly to be seen.

Chorus
          G                       
Love and joy come to you and to you our wassail too,
     Em            D          G           C
God bless you and send you a Happy New Year,
     G           D            G
God send you a Happy New Year.

(Now Verse and Chorus the same as above)

We are not daily beggars,
That beg from door to door,
But we are neighbours children,
That you´ve seen before.
We are neighbors' children,
That you´ve seen before.

....
    G          D           G-C (Change the strumming pattern according to the song)
God send you a Happy New Year.

  G             C           G                  D
I have a little purse it´s made of leather skin,
  G           C                 G                   D
I need a silver sixpence, to line it well within.
  Em        D                C       Em       D  (walk down the A-string again)
I need a silver sixpence, to line it well within.

Chorus

Instrumental
C Em D (3x)
C D
C Em D (3x)
C D

(Chords as above)

God bless the master of this house,
And then the mistress too,
And all the little children,
that 'round the table grew.
And all the little children,
that 'round this table grew.