Is it another bathroom you're putting in, or just moving the one thats already there? I know absolutely nothing about installing bathrooms apart from obv the plumbing will need to be moved, which I imagine is a pain in the ass - but im guessing a bunch of men come and do all that! I think if you're adding more bathrooms you need to make sure the drain can cope or something so dont know if it might need changed.
Thats it, thats the extent of my property programme information!