Hello Calum,
I'd just like to add that we are trying assess how well you are able to read, understand and integrate with an existing code base, because this is what you will be required to do when starting a new job programming games. Dropping individual files is fine, if you don't need them, but don't submit a project where every single one of the original files is redundant.
Additionally, if you drop an existing file and then end up writing something else that does almost exactly the same thing, then I have you assume that you didn't understand the original file.
Good luck, I can't wait to see what you come up with!
Lizi