If you are on a budget provide a square bath, against a wall and fit a shower screen (screens cost about £80. You can buy circular stainless steel shower rail that fix to the wall over a rolltop bath that serve a function, but they are not really satisfactory as the curtains get covered in black mould. i have been designing bathrooms for private clients for 5 years and have not yet specified a rolltop free standing bath, having owned one (although they look great!)