What engine does your car have? What age is it? Wha mileage is it? Has the belt been changed before? If so, at what mileage and what date? Did they change the tensioners, aux belt and aux belt tensioners?
Cambelt, balance shaft belt, and aux belt, inc all associated tensioners. Does it make a diesel sounding noise for a few seconds on start-up? If so, add a camshaft variator to your list. I wouldn't bother changing the waterpump.