The designer had done an fair job of laying out the bathrooms but it obviously isn't his speciality.
After talking to a couple of bathroom designers we came up with some layouts we liked and then had to ensure it all fitted together - enter google sketchup.
The picture below shows how simple this is, the background image is our floor plan that we imported in to google sketchup. Trace a view walls and then goto the sketchup warehouse and choose the vanities, showers, toliets etc. Position them and then play with the dimensions to ensure it'll all fit together.
