I guess that comes back to the original issue of inclusions. Different builders are going to require you to have a different amount saved for post-handover stuff.
My suggestion would be create a itemised list of everything you would potentially need to do post-handover. This will give you PHO Items list and a PHO Total (PHO = Post handover)
You would then be able to work out across different builders:
Total = Base Price + (PHO Total - Cost of any PHO Items included in build)
Hope that makes sense.