If your existing bath is fitted tight wall to wall, with little or no space at either end, then it is unlikely that one of the Whirlpool Bath Showers will fit into the same space.

You will need an absolute minimum space of 400mm at one end and 400mm at the front, to allow the installer to get down the side of the unit once assembled and behind it, to make the various plumbing connections. 

Once the connections have been made, the unit can be pushed back into the intended position.