Actually, we prefer to work with you during all phases of your writing process - from thinking to drafting to revising.  Many writers find that talking through their ideas with a tutor helps them to focus and refine their approach to the assignment before they even begin setting pen to paper (or fingers to keyboard).  Of course, we're happy to work with any draft of a paper as well - please remember to allow enough time for the tutor to work with you in the most effective way.