Remember to account for pipes, fixtures and other furniture items to ensure you have adequate space around the unit to access cupboards, open doors and drawers. Measure the distance from the finished floor to the centre of the waste pipe, and the location of the water inlet. Your plumber can help you to ensure these important measurements are correct.
The 'setout' of your toilet suite is the measurement of the waste pipe from the wall to the centre of the pipe. If you are replacing an existing toilet suite and do not want to change the plumbing, you will need to ensure that your new toilet suite will fit the existing plumbing.