Well, I did sleep after all - from about 3:30am to 7, on the semi-comfy chairs in our office that I nicked from the common room next door against this eventuality. And lo! my essay did not eat me. Indeed, I now appear to have reached that blessed point where word counts become irrelevant and it is now a matter of getting said everything that I want to say. Think it should work out about right: 500-1000 words to go; a couple more points to make and then a conclusion.