Ceiling Insulation

Foamex StyReflex with alloy foil layer in 40mm has an R rating of 1.10

http://www.foamex.com.au/polystyrene-products/styreflex

"... Designed and developed by Foamex, StyReflex™ is a clean, lightweight, non-sagging, non-irritant foil insulation sheet. Made from expanded polystyrene which has been foil laminated...  allowing for greater R-values to be obtained in open and confined spaces....
StyReflex is very cost effective and will not deteriorate, collapse, or lose thermal values over time. .."

Curved ceiling edge insulation

Fitted and sealed with expanding foam and taped up with insulation tape