Andy - we were in the same position. We found that sealed dried herbs and spices were OK.
A quick look around turned up these:
AQIS - talks about the Free Trade Agreement b/w SIN and AU - there's links to the AQIS site which talks about the import requirements TO SIN:
http://www.fta.gov.au/default.aspx?Fold ... icleID=222
And also look around:
http://www.ava.gov.sg/InformationForTravellers/
...which talks about import requirements.
Juniper berries might be an issue - better double check - there are contact details on the AVA site.
Note also that Mustafas, as well as a number of boutique places, sell a pretty wide variety of these types of things - however we're not experts and haven't done the full shop. Maybe somebody else can enlighten you more.
HTH - P & C
[Edited: Added Mustafas etc.]