Thanks to the magic of Java Script and CSS and all that sort of techo-stuff, I cannot link to the appropriate page, but this works...In a fashion ....
http://www.basix.nsw.gov.au/help_detach ... single.htm
On the LEFT, select Energy / Ventilation / Ventilation page
That's where I grabbed the piccys I linked to in the above posts.
(By the Power of Google, you could also try this http://www.basix.nsw.gov.au/help_detach ... llings.htm )
So yeah, Apart from those drawings, such as they are, I've got no other clues !!
P_D