Id ask the cabinet maker to adjust. There is a difference between firm and overly difficult to use. It is prob DIY with a screwdriver if you're handy.

I certainly feel more confident about the colour of the splash back, with a number of people saying they really like the colour. I'm quite confident now that I can enhance the green with an off white washable paint, or wallpaper with a little green and yellow highlights. Thank you to every one who has contributed to my query.

Those tiles are beautiful so I see why you favour them. They appear to be very similar colour to your brick pattern tiles. I think the ideal situation is to have the same flooring in both areas since they are connected and for cohesion. Maybe others will provide a different solution so you can retain the brick tiles as well as having new tiles. Have you seen Smartstone Athena? It would go well with a grey laminate (I'll have a look what's on offer) and Hogs Bristle wall colour. There's also another stone that is similar to Athena but the veining is diff colour. I'll have a look.

Looks messy, difficult and expensive. I don't know if you will have enough fall in the sewer pipe. I would suggest you get a sewer plan by contacting your local water authority, and perhaps a second opinion once you have this information. I would be asking about where the current laundry waste runs as this would seem to be a more logical connection. Best of luck, Dr Retro of Dr Retro House Calls