Im not sure how much brick is seen around the window frame, if its only a little brick, you could paint it, although I'd prefer it be a smooth rendered finishor plaster like your other finished walls, because if there are three surfaces visible in there, none will be a feature, and all will look incohessive. To let the ply wall take the focus the plaster is perfect in contrast, so if absolutely necessary, pair. He brick white, although my recommendation is to gy rock and paint, just with he back wall in marine ply. Good luck, I'd love to see your finished result. By the wY, mentioned split battens to hang the ply, if you're unfamiliar, it's where timber battens are cut in half on the diagonal through section, and one half is fixed to the wall, the other the ply sheet, when they go together they become a secure locking fixing. Any handy person or tradesman will know how to do hat, without glueing or messing up the brick wall. It's quick, cheap and secure, and best of all can be removed without much effort to allow you flexibility in time.

Any pictures?

Hi all, it's now 2020! I'm at render stage and would love it to be white but the renderer I spoke with this morning said to think long and hard about 'white! as it gets dirty very easily especially taking into account the recent dust-storm, not to mention the ash and smoke from the ongoing bushfires. I would like to know: how your respective white renders are coming along in regards to appearance, staining and maintenance; and what type of render and render finish do you have? I am looking at a sandy Rokcote acrylic render. Any feedback would be greatly appreciated!!

If you want to make the house hotter, then painting the roof charcoal will certainly achieve that. Repointing the brickwork is the most sensible from a maintenance perspective. Once you render and paint, then you have to keep painting (and it's likely to be out of fashion sooner or later). Try to keep passive cooling in mind (i.e. light colours & permeable landscaping) with any of your renovations, and I think it always pays to try and embrace and compliment the original architecture and be unique, rather than trying to look like the latest project home. In my opinion the arch window is actually quite cool, and the excellent mock-ups provided by Geo Toria are along the right track.