get the plastic lid of an icecream container-cut the thick edge of 3 sides. slip the lid right under the edge of the mirror, and it will stop paint getting on wall. we use this for skirtings all the time, works a treat. just remember to wipe the back of the plastic every now and then, in case you collect any paint on the back.

We have the black mirror splashback. We love it and it soooo easy to clean

I agree with Diane's ideas! Grey is a nice color. The only thought I had on having a corner sink cabinet, you may not be happy with it in the end. You have a little corner, and the sink may be too small for you in the end along with not having any storage space. If you can't find any curtains that you love, try a cheap roller blind for now. It will give you a visual look and an idea if you want to stay with a curtain or going a bit modern with a patterned blind or even a roman type shade. It could turn the cozy look into a clean modern look. Framed mirrors are expensive. Call a glass company in your area and have them give you a price on mirrors. It might be quite nice to take the mirror down, and replace the wall there with a complete wall mirror to fit, stopping the mirror at the vanity, and continuing the mirror across the vanity between the sink and window. It will make your bathroom feel much bigger, even though you wont be able to see in the mirror over the sink. Close up the vanity doors with new door. Use props first (white poster to cover up the doors) etc. before you buy anything! Stick on tiles are a great idea! They clean nicely and look great. Although I wouldn't go with the wood look. Your bathtub tiles are old fashioned, go with a stick on floor tile that is easy to look at, try to get samples first. Remember Gray is a sleek clean modern color. It is not a cozy country color. If you don't like the grey in the end, maybe a real pale blue or butter yellow (that would be more of the cozy cottage look).

When we lived in Australia, we had exactly the same problem with our children's bathroom. We changed the wall between into a low pony wall, and converted the window behind the toilet into a storage cupboard for toilet paper and other bathroom supplies. We also put in a pocket door like you have and a fresh new shower curtain over the bath/shower. I've attached some photos which I hope helps.