Hi Glynes,
The act 556 (1) (h) land that belongs to a public benevolent institution or public charity and is used or occupied by the institution or charity for the purposes of the institution or charity,
I believe they would have to be using the property or occupying the property as per their mission statement and articles of association. They would not be able to complete their objectives ie in a semi-built facility, so therefore rateable until the property is being used for its purpose.
Just my thoughts.
cheers brigitte.