Help me land an SA!!!

I've got a good resume (i reckon better than 99% of SA applicants), apart from my academics! I got bad a-levels (end of high school exams in the uk), which is 320 ucas points, this is above the threshold banks ask for when applying, but lots of people will have 480. I do have 'mitigating circumstances' in that i fell ill about 6 months before my exams, was an out-patient at a hospital unit, and had to pull out of school. So i did my best to teach myself, whenever i could, but it didn't really work and hence my results were well below par. I got into a reasonable uni (non-target, but they still accepted me given my circumstances) but i had a Cambridge offer for maths prior to this.
Do i include something about these circumstances on my cover letter/elsewhere? I REALLY don't want sympathy, or to seem like a whinger, but at the same time it's genuinely why i didn't get good results and into cambridge. How do i word it?

So on my resume apart from academics is; i'm a former national track champion and have run the 2nd fastest time in Irish history over 800m for my age, i'm on my university cheerleading team and investment society, i've had work experience and 4 BB's, and a day's work experience as GS, i started my own company at 16 and made more than enough money to pay all my uni fees, and i'm interning at a large fund this summer. I've reallyy made an effort with my CV to try and counter my a-level results.

If you screen SA CV's, let me know what you think my chances are and what I should do from here.
Thanks