The door into ensuite currently opens in (hinged on left). Im thinking we will need to use a cavity slider door (which means shifting the bedroom light switches!) This project is growing!

Reconsider not having a bathtub in your large master bath space, which currently has a good bit of wasted space, for your convenience as well as for future buyers. You also don't appear to have any counterspace or storage by the sinks, the shower is big enough that you don't need a door on it, and a small freestanding soaker tub could fit under the window in the wet area of the space if the door to the bathroom was moved a couple of feet up the wall opposite the sinks. You can't put furniture on that wall, anyway, due to the traffic pattern.

I would not recommend glossy tiles in a bathroom. We have 24" polished porcelain throughout our house, and... we also have a pool. Although I love our tiles, I have to be super careful coming inside. If I am at all damp, walking on the tiles is tricky. Yes, they are easy to keep clean, but so are most tiles. For my master bath, I went with tiles that had a high COF (Coefficient of Friction). I've had my fill of slippery bathroom floors, and wanted something that I didn't have to slide a towel around on. I love them! I can step out of the shower, and have as much grip on the floor, as if I had stepped onto a mat. :)

Add colour . Please add colour haha . Just a thought though , instead of paint ( its a bit hard for me to visualise everything from your description -- I am a visual person ) how about maybe those translucent blue looking tiles ( yes , I know , extra cost ) , you may even 'frame' them in the white tiles to tie in with the shower , or possibly do the blue instead of the white , or even do the shower in them , and have the rest your 'white' walls . And when I say about those tiles , you can get them in square or subway or even long skinny ones , or even long and skinny but with long skinny darker blue and brushed ali ones too -- in other words , have fun and add interest !