"it was quoted the Centro Halls head had a 50% occupancy rate"
Which page of which document?
Page 18 of this document (titled Centro Properties Group
Supplemental Information First Half FY08 Period ended 31 Dec 2007)shows halls head as 100% leased.
http://www.centro.com.au/NR/rdonlyres/C065768E-08DE-4626-8137-AB25D56E3F06/0/CNPSupplementalDec07.pdf
Centro Halls Head 50% CER / 50% CAWF Halls Head WA 2001 2001 6,037 100% (<- percent leased)