Stephen,
Jacque recommends: Scott McGeever from www.propertysearchers.com.au
Very experienced ex-valuer, knows Brissy like the back of his hand.
She made a post here: http://www.somersoft.com/forums/showthread.php?t=47644
hansal, like most professions, a recommendation from someone who has used their services speaks volumes.
Ask for references or read their client testimonials would be my suggestion.