Thank you everyone, your thoughtful advice was very welcome. I'm attaching a photo as its all finished. I selected Olive Reserve for the splash back and painted the wall above it the same colour. As its a big room with lots of light and a large window it doesn't dominate. The glass is so easy to keep clean and I love the way it reflects the garden and light. Have to say though some people are stunned into silence when they see it, but as the cupboards and bench tops are quite bland I knew something bright was needed

Sounds like a very stressful situation! If there is absolutely no way the builder will allow you to change things (even if they did, I imagine they would ask you to foot the entire bill of pulling the tiles down and replacing all water proofing in addition to new tiles), I can make a few suggestions for improvement. Firstly I would suggest replacing the tiles above the vanity with a white mosaic, a patterned or a textured feature tile/strip. You could also use this same tile to replace the vertical feature in the shower. There are some beautiful shapes and sizes available to choose from. Secondly I would address the grout situation in this way: Floor - dark colour grout & Walls - Light colour grout. Lastly if it does not prove too difficult or expensive, maybe replace the tiles below the vanity with a plain white tile (could be similar size). Good luck and I am sure once you have a lovely mirror up and some crisp white towels, it will look just wonderful.

The cracks are in our walls though I note our old tiles in our bathroom floor have lifted slightly so I suspect cracking may be an issue for us?? But I will explore the polished concrete/terrazzo option if you think it can be overcome as this is certainly our preference. We moved into our home recently and have basically lived downstairs so have not used the bathroom upstairs at all. A guest showered in it one time and it leaked through to our bedroom ceiling!! So we suspect there is an issue with the waterproofing and there are cracked tiles however we won't really know what the issue is until we pull it all out to see what is happening under the tiles. Thanks for your comments Ann I've appreciated your insights - good to talk with someone who has actually lived with these floorings rather than just going on what you read or are told by a salesperson.

painted glass will be a perfect solution for your dilemma...my parents couldn't afford a solid bathroom door and solved the problem by painting a glass door with a dainty pattern by dabbing the brush rather than using sweeping strokes...paint lasted for many years and never needed redoing and i think a simple couple of coats to cover any missed spots will give an excellent result without any extra preparation than the usual wash and dry the surface and protect against drips