T Rex — Ballrooms Of Mars Chords

Ive been trying to find a tab of this for ages, so i thought id have a stab at it..
This is main riff pattern that i think is just played over and over throughout the song.
Its played quite loosely, i prefer to hit the bass notes of the chords then strum the
higher notes slightly afterwards so thats why the chords appear slightly off—kilter.
Havent got a clue what the A? actually is, sounds a bit diminished but not sure....anyway
hope its ok!Enjoy!!

RIFF 1

   C      B/C     A   A?
E—————8————————————5——5
B—————8————————————5——5
G—————9————9———————6——5  substitute the A? (dont know what chord that is)
D———10—————10—————7———6  with a standard barred D chord
A———10—————10—————7———6
E———8——————7——————5———5

               C   B/C              A      A?
You gonna look fine, be primed for dancing

          C              B/C                 A    D
You gonna trip and glide along the trembling plane

REPEAT OVER FOR REST OF SONG I THINK

Substitute the A? with a standard barred D chord when you get to the end of the second line ie 
E—5
B—7
G—7
D—7
A—5
E——

This is my first tab but i think it sounds ok.
Dont ask about the solo, i cant double track with an acoustic!
Any suggestions, opinions send to matt@moodguru.co.uk