Although we tiled our kitchen with tied mosaic sheet I would also consider glass splash backs, they are so much easier to fit and keep clean for your layout. The people we bought our splash back from did panels to size and cut outs for electrical sockets. You just use the provided glue to stick it to the wall. I think they were called something like ‘premier range’ but we found two different suppliers online and went with the best value. We also found anti bacterial plastic sheets online which came in a range of colours. These are designed for commercial kitchens and used these to smooth off a wall behind our fridges and freezer. These would also be good as you can cut them on site and stick with siroflex grip and grab adhesive.

Thanks for responding Daisy! What worries me with the bold swirls of the worktop, is that the upstands may not 'match' properly? So areas of the worktop that have a darker part of the pattern, could be edged with an upstand that is from a lighter part, or if the direction of the swirls is different between the upstand and the worktop. I avoiding marble tiles in bathrooms etc for similar reasons - it would drive me nuts if the veins don't line up or go opposite ways!

The chances of finding tiles this size is very slim, unless you find someone who resells old tiles. I would suggest using a mosaic like Daisy has said above, or at least something that is a completely different size.

Thanks to bad renovation timing coinciding with the start of Covid lockdowns, we used DIY removable wallpaper above our upstand as a temporary “make do” measure because all work and shopping had to stop. Three years later (!) we are finally getting around to removing a chimney breast to completely finalise the kitchen, including replastering, and I am fairly certain I will be using the same wallpaper again. The only difference is it will be professionally hung! We have received so many compliments and it’s been shockingly robust, even behind the hob. We used a greyish shiplap patterned wallpaper above a Carrera marble countertop and upstand, with white upper and pale grey lower cabinets.