In reply to mat cooper:
Take something heavy to your climbing wall with you when it is quiet, untangle your rope, lead it up (an overhang) and then tie off one end to the ground anchor and hang you heavy object off the other end.
Leave for 15-30mins, boulder. The rope will slowly unwind itself removing the kinks. When your suspended heavy object stops spinning, pull some rope through and unwind the next section of rope.
This will p+ss people off if it is busy thou. it does take a little while to untwist.
Once untwisted it should not knot itslef again so easily if you coil it properly and don't use friction hitchs etc.