Hi Rosa - I had a look and unfortunately I couldn't find a link. They were the same shape and size at the metro tiles, but matt white. Definitely from Topps because I chose wall and floor tiles from there in the same trip. Not sure they still do them, but someone will have something similar at least, surely? I was sad to leave that lovely kitchen for the shitty little one we have now.
Porcelanosa usually have a range of tile finishes so maybe they have something?
I think with a brand new kitchen I would lose the wallpaper and take a fresh look - or maybe keep it on one wall if it's on several now and you really love it. It depends what kind of look you are aiming for, the natural light in the room, etc. You could take one colour from the paper and use that on the walls. You don't have to stick to one tile colour either - you could add rows of a different/stronger colour in the same tile. I would steer clear of mosaic as I think it's had its day (although some of it does look lovely) and there's lots of grout to clean between the little tiles!
Not to everyone's taste, but Kelly Hoppen has some good ideas for really lovely combinations of muted colours and different textures and you can add stronger colour to that. Your cream kitchen will work with lots of different things. Sometimes very modern can look really good against something with a vintage look - I'm not saying shabby chic because I don't mean shabby!