@"Paul Caint" good call! sorry I was late to the discussion (I just finished the test in Asia). You won't lose anything by not cancelling (you will have access to your answer sheet and look up your weakness).
I didn't ... make a good case for cancelling. If you didn't do ... . That's the argument against cancelling. That said, if you know ... chance of a low one, cancelling can probably be justified.
If I were you I would be studying with no music in a public place. Like a library that is sort of busy. This will get you used to tuning out randomized outside noise.
@"Paul Caint" good idea on the neutral noise! I don't like studying anywhere too quiet because it's certainly not what test conditions will be like either.