It's the floor colour that's the main problem, neither one thing nor the other, and certainly wrong with the benchtop. Leave the wall tiles if you like that sort of thing and find a way of covering the floor probably with laminate planks on an underlay. We have a European Birch golden coloured timber floor but softer grey splashback and it looks fine. It's not an award winner but the floor and cabinet carcases had been there twenty years and it was affordable. Don't even think about painting the floor or putting down mats but a clear plastic runner in front of the sink works well for us.

I went vertical so tall. Helps to raise height. It will also match your 300 floor tiles I have silver grout with antique white tiles. It’s a personal choice you can’t go wrong either way.

I suspect that you may find that they are difficult to remove as single tiles. Maybe consider a crazy, random pave pattern for your bathroom floor made up of broken slate tiles? Similar to this photo but on the floor: Make sure you have a suitable waterproof membrane underneath to comply with the Australian Standards and you will have a lot more grout between the slate than a traditional square tile pattern. Best of luck, Dr Retro of Dr Retro House Calls

If the hexagon tiles are to be the feature then the wall tiles should not draw attention to themselves. I would go with stacked horizontal as this will make the small room seem wider and it will be a simple grout pattern that won't try and compete with the hexagon mosaic. For small bathrooms understated and simple always looks cleaner. Best of luck, Dr Retro of Dr Retro House Calls