If nothing else, I can supply the chords:

  Chorus
  Ab                  Cm
  Seven hundred elves from out the wood
  Ab       Bb        Csus4
  Foul and grim they were
  Ab                   Cm
  Down to the farmer's house they went
  Ab           Bb       Csus4
  His meat and drink to share
  
        Bb    Cm                     Bb       F
  There was a farmer in the west and there he chose his ground
     C                    F      G         Bb          F
  He thought to spend the winter there and brought his hawk and hound
     C                     F         G     Bb      F
  He brought with him both hound and cock alone he begged to stay
      Bb      Cm                            Bb       F
  And all the deer that roamed the wood had cause to rue the day
  

Source: The songbook Steeleye Span: Original Masters,
(c) 1977 Steeleye Span Limited/Chrysalis Music Limited.

If the chords (in the key of Ab) are a bit impractical for the guitar, no doubt they can be
transposed easily.


As for the background of the song, the songbook simply says "traditional". It has no notes on
the songs. However, the link given by Brendy above (scroll down to the middle and a little bit
more - the passage starting with: "A lot of our mythology came from the Danes")
suggests that it was adapted by Bob Johnson -
the chorus and the tune? Furthermore, I have the 2 LP set "Original Masters" that correspond
with the songbook (it is a compilation), and it gives the following credit: "Adapt. from Trad.
Words; Music by Hart - Prior - Knight - Johnson - Kemp - Pegrum). So there is another piece of
the puzzle for our experts to work on.