Dont worry. im in the same situation as you are.
I dont even see why i chose to study further maths this year, because really dont find the subject entirely interesting. However, i think its ok to say that if you have at least tried during the year, to further your maths knowledge, then i'll think you'll be safe.
This year in my class i sit next to these two maths geniuses, who will have no problem getting 50 and it makes me feel bad, for someone only averaging B-A's in SACS, so i know how you feel!
When i approcahed the business maths module, i kinda gave up because it looked so daunting, but at the end of the say all you can do is give it all you've got.
But look at it this way- if further is in your bottom 2, then the difference between a 20 and a 25 is NOT that large.