If it's actual marble, then it will have been more than likely etched by the acid in any urine that's been in contact with it and would need honing then polishing (which may sort the grout too if it's only surface dirt). If it's just dirty ceramic marble-effect, then high alkaline and some elbow grease - the grout would probably end up being the hardest to clean and would benefit from grout colouring - recommend that they change any white grout to grey on a floor and it will stay looking clean a lot longer.
edit; Sorry, should have added that Aquamix make all the products you'd need for either type of floor, and although it might not be the cheapest option you can at least get hold of them easily enough. You'd need Knock Down for honing, Renue for polishing, and Concentrated Tile and Grout Cleaner for cleaning. They also make a good epoxy grout colourant, though it's a bit of bitch to work with.