Hi there, I would definitely go for glass & not tiles. Glass is much easier to keep clean! As for colours, if you have French grey units you could look at a slightly iridescent silver which would compliment well. Be careful with some colours if you are going to be a bit bolder as they will reflect & alter the appearance of the French grey on the cabinets. Get some samples & look at them in different areas under the units - the corners will look darker/lighter depending on natural light & if you have recessed lighting under the units.

Tiles are one way to introduce some pops of colour in your kitchen. If you are worried about the grout discolouring, use epoxy grout which is more resilient to liquid staining. Also, if you use a coloured grout, discolouration will be less noticeable. If you choose textured tiles with rectilinear edges, grout lines are almost invisible. Using tiles can look more traditional compared to glass or stainless steel. The problem with stainless steel is keeping it looking good. Drip marks and grease are instantly noticeable. Glass is less obvious when splashed. They are both more industrial and modern looking. What about using the same material that makes up your worktop as the splashback? Most manufacturers of manmade worktops also do an 11mm thick splashback and upstand.

Thank you all for the feedback. The gaps between the brick slips would be the same as between the bricks Colourhappy. It sounds like the marble quartz is winning! It does look lovely, I just wanted to make the most of the bricks on that wall too, but in practice they would probably be a pain to look after behind the hob. Thank you for the compliment Lifestyle Kitchens, I'm excited to see how the finished kitchen turns out.

I personally love tiles. I think they add interest. However I had to google Wow Fez tiles as I had no idea what they were! So they are Moroccan hand made style tiles and you are wanting plain white ones? Is that right? Are they like the ones in my second pic? If so, I think they are beautiful. I think metro/subway tiles are a bit boring unless they are an interesting colour. I would tile behind the cooker and up to the window sills. However some people have just an upstand in the same material as the worktop (picture below) and use a washable paint on the rest of the wall. It boils down to personal taste.