The Basic Rhythm
G -----------------------------------------------------------------
D -----------------------------------------------------------------
A -----------------7-7-7-7-7-7-7-7-5-5-5-5-5-5-5-5-----------------
E -4-4-4-4-4-4-4-4---------------------------------7-7-7-7-7-7-7-7-

Chorus - "In The Caves All Cats Are Grey..."
G -----------------------------------------------------------------
D -----------------------------------------------------------------
A -3-3-3-3-3-3-3-3-2-2-2-2-2-2-2-2-3-3-3-3-3-3-3-3-2-2-2-2-2-2-2-2-
E -----------------------------------------------------------------

G -----------------------------------------------------------------
D -----------------------------------------------------------------
A -3-3-3-3-3-3-3-3-2-2-2-2-2-2-2-2-3-3-3-3-3-3-3-3-2-2-2-2-2-2-2-2-
E -----------------------------------------------------------------

G ----------------------------------
D ----------------------------------
A -0-0-0-0-0-0-0-0-0-0-0-0-0-0-0-0-- repeat until end
E ----------------------------------

A Possibility... follow the keyboard a few times and then slowly drone
into the "A" like so:
G ------------------------------------------------
D -7--5-------------------------------------------
A -------2-3--------------------0-0-0-0-0-0-0-0-0-
E -----------1--1-1--1--1-1-1-1-------------------