Honestly, unless you have a really good reason to suspect that your paper/s haven't been marked properly there is not much hope for a successful appeal. Your paper/s have been marked twice by different examiners who have both come to the same conclusion - that you fell just short of achieving enough marks for that C. As frustrating and disappointing as this is for you there does have to be a cut off point somewhere and unfortunately you have been marked at the wrong side of that point twice. Appeals are rarely successful in cases like this where the two examiners have both awarded very similar marks. Sorry I can't give more positive advice about the appeal, however, with regard to your place in one of your lessons being questioned you should definitely plead your case. You were very close to that C, and really does the difference of just two marks mean that you are less able - of course not!