Vaalia is a staple. They say on their site no artificial preservatives, flavours and colours and they mean it. Their snack sizes are perfect for the lunchbox and quite safe. They are more expensive than your more recognised brands, however IGA and Woolworths stock them cheaper than Coles.
I also recommend Chobani yoghurts which come not in packs of 12, but as individual round tubs. Often they will be on special for $1 a tub.
Do you have a yoghurt that you regularly eat that is chemical free?
Note: After the publishing of this blog post I have since discovered that Vaalia has now added Carmine to their Berrie Flavours. Avoid this flavour if you exhibit sensitivities to this natural colouring.