This explanation may help, Source: https://www.renovatorstore.com.au/blog/lighting-and-power-in-your-bathroom-the-simple-rules-to-be-safe/ REQUIREMENTS Zone 0: Inside the bath or shower. Any Lighting used here must have a minimum rating of IP67 (protected against immersion in water) Zone 1: Above the bath or shower to a height of 2.25m. A minimum rating of IP44 is required Zone 2: The area stretching to 0.6m outside the bath or shower and above the bath or shower if over 2.25m. An IP rating of at least IP44 is required Outside Zone: Anywhere outside zones 0, 1 & 2. Where water jets are not to be used for cleaning purposes, the general rules of BS7671 apply In addition to the above, if there is a likelihood of water jets being used for cleaning purpose in zones 1 and 2 a fitting rated a minimum IP65 must be used. Now that this has been explained, always make sure to purchase bathroom lighting according to these standards to make sure that your bathroom is always safe. You should also have this principle applied when you purchase other electrical devices such as heated towel rails, or a guide to where you'd put sockets in your bath for razors and other devices. This may also fix the common misconception that LED lights are not rated for bathrooms. Typical LED lights have an IP rating of IP66 which is more than the needed IP rating standard that bathrooms should have. - Not to mention you'd be saving a whole lot from energy bills in the long run.

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.

by "other options" i mean that you should consider all other options for locations of fixtures..there is already plumbing along each wall so swapping the location of shower and bath or vanity isn't as challenging as if there were no original plumbing in that area and if you plan to replace the fixtures and tiles rearranging the fixtures will only be a small percentage of the budget and it's a shame to limit the final result without at least considering other options..and although there is enough space to have the vanity hard up against the wall my suggestion is to have the vanity away from the wall to make it easier to clean and also because the small nook is an ideal space for hanging a hair dryer and with the luxury of so much space it will be easier to install a vanity away from the wall

I just think if everything is jammed in tight it won't seem relaxing and you won't use it. When you consider what you use every day (vanities and shower) I wouldn't compromise them for a maybe-once-a-week-if-most dust catcher like a bath unless you had heaps of space.