This may seem a stupid question but can I tile on top of this tray, is this it’s purpose.
This questions is absolutely crucial and constructive.
Yes, those trays must be tiled on. They are not finished products. They always need to be tiled on.
You can use other materials like mosaic or marble or stone, as long as it's not thicker than 15 mm. If they are, Showerlay Invisible is the range of the product you should be looking at.
David M 020 7193 0953