OK, definitive answer time:
The space above the wheel brace IS for the removeable towing ball.
The space at the top is for the aerial diversity switch box, fitted as standard on all 2002 models with either a Symphony2 or a Concert 2, but NOT the Chorus 2.
The space underneath this is where the Navigation unit was housed if you ordered the basic nav. package or, if you ordered the Navi.+, the cd for navigation was in the headunit and this space was then free for a tv tuner, which was an option for this headunit only.
Cheers,
Mike