I would recommend going a darker colour too! We have done it several times with clients who (like yourself) can't see what the finished concrete aggregate will look like until afterwards and the darker the better we have found. Like Zaffa said, it would be amazing if you could extend the concrete into the bathroom, as that can be absolutely beautiful and this aggregate look is a fantastic addition to a bathroom. However if you want to break it up I would go for a dark charcoal (large format) tile so you don't risk clashing colours. Darker bathrooms are really stylish so you don't risk sacrificing on style. Don't hesitate to contact me if you need any help selecting specific tiles as we know how overwhelming it can be and are happy to help. Best of Luck, Jordan from JFI Studios!

I will be the loan naysayer and go: Vinyl Plank timber pattern tiles. I did these in my kitchen and they helped make the room. Used Karndean, but any European brand should be fine (avoid American and assume they are using American or worse if they don't say the country of origin). http://www.karndean.com/en-au/floors/landing-pages/new-looselay-longboard?gclid=CjwKCAjwspHaBRBFEiwA0eM3kQ7eEFPH5FlK2IwV3o7ZsbbmJ19srG0OM_tWK5dhPMNyDdwxGPUr4BoCoYcQAvD_BwE Caveats: Ground must be FLAT. 100% flat, ruler FLAT. If not you will have to level. If flat, you can lay them yourself. Our floor had to be levelled and it was tough. still got a few high patches and gaps because of that. However I have done it on a concrete surface myself since and it's beautiful. Benefits: Nice and soft on the foot. (less ankle pain) single tile replacement. Looks fantastic. No PVC glue fume issues and fairly resilient. Do be wary though of metal chair legs scraping the floor. Waterproof! when installed right with no gaps! (why I would choose them in a kitchen over timber or Eeek carpet!.... Yes previous owner installed shagpile carpet in the kitchen).

a section of the floorboards can be removed and install compressed cement sheet in the hallway and the waterproofing extended over the new flooring and tiles laid over the original floor and cement sheeting without needing to pour an extra slab

Talk to a concreter. Will the thickness of the screed fit under your doors and March any transition to other surfaces?