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/

To Modernise this without rendering or retiling the roof I would probably recommend to go darker with the trims. My top pick as a colour consultant would be Dulux's Domino for the trim. It will be a little bolder and create a more modern contemporary feel. You can see it pictured below as the trim. Obviously this house has painted their bricks in the shade "teahouse" however it will still look much better on your 1980s "peru" colour bricks! Don't hesitate to contact me if you need any more help colour wise!

are the new sliding glass doors double glazed? are the original windows single glazed or in need of replacing for any other reason? do you hate the beige colour? how many of the old windows can be seen at the same time as the new doors? ... inside looking out is the most important view for me but what do you like the look of?

As said by big reader...leave white or paint the same colour, without the brushed finish, on the other walls. You can not bring another colour in. There is enough colour already with the orange wood and the bed cover. Also, the curtains look too small to pull right across your window correctly. They should be waved not flat when closed.