You could try a foil backed plasterboard dont plasterboard board to the floor, leave a 2 inch air gap at bottom.
Even if you plaster a wall leave 2-3 inch gap at bottom
Then use upvc skirting boards
(Bewary with rock wool idea put a piece in water it acts like a sponge i would not use it if its a very wet wall)
Or you could use a tanking plaster something similar to this and plaster the wall, would always use a small dehumidifier in the room with damp problems and if you leave door open will help rest of house,you will be amazed how much water they remove
http://www.sovchem.co.uk/tanking/plasters-renders/25k-ready-render-rd.html