There is a comprehensive guide at the Bluescope website at http://www.steel.com.au/products/coated-steel/colorbond-steel/basix-and-bca-classification

I just googled & found this site, which quotes cost of R2.5 75mm. there are other suppliers as well. What was quoted to you for cost of roof installation, and was it itemised so you can see exactly what thickness the foil-backed insulation builder will use? I'm guessing the thinner (lower R factor). So, the new quote should reflect a credit for the cost of previous insulation, since it won't be used, then cost of thicker insulation added. Does that make sense? If you are unsure, best to speak with the builder. https://www.pricewiseinsulation.com.au/product/heavy-duty-fletcher-permastop/

Yes go monument!and if you go for some lime acacias out the front (tall weeping or the low bush)it would brighten up you whole look.Also adding strappy green plants that bulk up would give it a bit more of a clean look. If you don't want to go monument on roof go a light grey and tie in with a couple of tall light grey planters on either side of your door. Pleas please please!find someone with a jigsaw and cut the tops off your pickets to give a cleaner look before you paint them. I'm stating the obvious but those security screens are pretty overwhelming,can you just have them on windows that can be opened,it might not look so busy out the front.

Look at Monument instead. Wallaby looks ok but I don't think it works so well with your brick.