Changing straight staircase to a turned stair with half landing, is this the Only solution to stairs cutting loft in half?
If the stairs to the attic don't match the stairs to the second floor you're most likely going to wind up losing floor space on the second floor. How much depends on how many steps change direction. If you do change the first-second floor stairs to match you're going to lose some room in one of the sitting rooms. That might not be a bad thing because really... how lazy do you need to be to have two rooms dedicated to sitting? :) Your heart and your doctor will be happy but your renovation budget... not so much. 

As to being able to fit a shower room... That can't be answered without seeing the floor plan.