wetroom to concrete floor

yes you need more than a plumber as it will need the floor concreting and a damp proof course between the walls. there is a variety of ways to complete wet rooms i would recommend looking into these options a pick one u prefer.I would advice using surface mounted plumbing in case of leaks as it is easier to access the piping. Chrome piping is readily available and looks great.

Yes, if you are having tiles you will need a tiler with wetroom experience to waterproof / tank it correctly.