This is an old English carol which Blur gave away at a free gig in London in 1992 (read more about it here ).
Again, as far as I can see it has never had a commercial release (you can see who sang which part here). Interesting to note at this point in their history, Blur were considered washed-up. Over the next three years their story would change utterly.
I have attempted to investigate ‘Wassailing’ and the origin of the song, some sources indicate that Wassailing is to do with drinking good health to one another – but various internet sources point to the song being from either Sussex or Gloucestershire. So any firm info would be much appreciated.