EDIT

Hi. I didn't go to Kings (I'm an UCL grad) but my wife did. Exams do happen between June and July (at least they did in 2011 - if my memory serves me right). Once you're done with your exams (this should be around mid-July), the time to write your dissertation begins. Of course, you can start to work on it before that. Unfortunately my failing memonry doesn't let me give you more precise information, but I hope it helps anyway...