The following are available; https://www.thewoodveneerhub.co.uk/products/fraxinus-black-ash-crown-cubeflex-pre-finished-psa-peel-and-stick-wood-veneer (not sure if this is real veneer though, sounds like some sort of laminate) https://www.thewoodveneerhub.co.uk/products/black-tulipwood-coloured-wood-veneer (not ash but may be similar enough. Another option would be to buy normal ash veneer and stain it, it's real wood after all. I'd test this first mind before buying loads.

you could look at these https://www.houzz.co.uk/professionals/carpenters-and-joiners/c/Edinburgh--City-of-Edinburgh

The green and the blue work well together to create an interesting colour palette, if you combine a few more of these colours together in the room such as with cushions, throws and accessories it will help it all make sense😊 We would love to help you, create a room you'll love to suit your style and budget! Here’s our website if you would like to take look - https://www.thelivinghouse.co.uk/

I just found these companies: This and this I might try to do it myself. However, I can't see the hinges they use. Any thoughts on what sort of hinges to use to make sure they are not visible? The door would open outwards (into the hallway).