Try these from Mandarin Stone, my sister used them in her kitchen and bathroom and they looked stunning. This is becuase they are not a flat colour and the edges of the grey looks soft, almost like an etching. They work well with greys and Skimming Stone paintwork. https://www.mandarinstone.com/product/monochrome-decor-porcelain/

Keep the layout as is. You need a new modern toilet (more water efficient) a new basin/vanity if you can find the right size, something quite narrow and at least a new bath panel. I would change all the taps too at the same time. I'm not sure what the flooring is, or is it a mat? Either way I would replace it. That extractor vent is filthy and needs replacing urgently. Not the greatest space for a basin but would probably cost a lot to move. At least you can use the window ledge for a mirror. You could also have a round mirror on a pull out bracket to the right of the window.

Do you have any inspirational pics to share? We need to get an idea of what floats your boat and can advise you from there. What's on your wishlist? It also depends on your budget. Leaving the plumbing in situ and updating the fittings is usually the most cost effective update unless there is an obvious layout clanger.

https://www.elledecoration.co.uk/inspiration/bathrooms/a43389551/mount-sapo-bathroom/ I would look at Retrouvious and it's founder Maria Speake's work, some lovely original ideas. The bath is stunning and I love glass blocks.