My first essay was an eye opener. Everything seemed to have changed from how I remembered you were supposed to do it. My advice would be to do your best with the content and expect to have some feedback on structure. The biggest surprise for me was to find that I was advised to go what I see, as all Sun journalist on every paragraph, and start each with a one sentence headline style summary and then put the content in. The second essay I did I seemed to manage this by writing a paragraph then taking the final sentence I’d written for each one and put it at the top!
Definitely reference as you go and bibliography. It’s taken me five years to realise what good advice that is, and to put in the bibliography things you don’t explicitly refer to in the text but draw on concepts from.
I always write about 30% more than the word count and then step back and pare it down to what the most important bits are, what actually makes the case.
I’m on my sixth year and it hasn’t got any easier … but at least now I am at the concorde fallacy point where I’ve put so much time and money in I can’t stop regardless of the reward / outcome!