Are you using the crustacean style? Changing your essay writing from the small scale up will show the quickest short-term changes, which in turn ought to please your markers. I haven't read history since 2007 (now I have the joy of writing physics essays,ugh) so I doubt I can help with more than writing style. I'll see what I can dig up on primary and secondary source usage if you like, but classics probably deals with them quite differently to modern history. Good luck with the essays!