Not familiar w/ OC&C; if they are like most consultancies however, they will understand you do not have a business background and won't assume your knowledge in that area is extensive. Still, you are right to want to become familiar with a few concepts. Here are some that should be easy to grasp:
1. Difference between assets & revenue; cash & cash flow; balance sheet & income statement
2. HIgh level understanding of profitability driver. Think here of the structure Revenue = (Price x Quantity) - (Fixed Cost + Variable Cost)
3. Know how to calculate the break-even
4. What type of divisions are in a typical company: Finance, Marketing, Operations / Back Office, Custoemr Service, Legal, Communication. What does each do?
5. General business environment knowledge, read the Times & whatever other economics paper you get your hands on
Last but not least - have you prepared case interviewing? If not, I strongly suggest you kick it up into gear and get busy on this. This will be the most important skill you can display, by far. Victor Cheng's 6 hours of YouTube video is a good place to start, PrepLounge also has some very solid material. Given how little time you have left, I'd also strongly suggest you work with a coach: doing cases with fellow candidates will not be enough without pointed and actionable feedback adapted to your specific needs.
Congrats on scoring the interview, good luck now in the prep.
Not familiar w/ OC&C; if they are like most consultancies however, they will understand you do not have a business background and won't assume your knowledge in that area is extensive. Still, you are right to want to become familiar with a few concepts. Here are some that should be easy to grasp:
1. Difference between assets & revenue; cash & cash flow; balance sheet & income statement
2. HIgh level understanding of profitability driver. Think here of the structure Revenue = (Price x Quantity) - (Fixed Cost + Variable Cost)
3. Know how to calculate the break-even
4. What type of divisions are in a typical company: Finance, Marketing, Operations / Back Office, Custoemr Service, Legal, Communication. What does each do?
5. General business environment knowledge, read the Times & whatever other economics paper you get your hands on
Last but not least - have you prepared case interviewing? If not, I strongly suggest you kick it up into gear and get busy on this. This will be the most important skill you can display, by far. Victor Cheng's 6 hours of YouTube video is a good place to start, PrepLounge also has some very solid material. Given how little time you have left, I'd also strongly suggest you work with a coach: doing cases with fellow candidates will not be enough without pointed and actionable feedback adapted to your specific needs.
Congrats on scoring the interview, good luck now in the prep.
Case in Point: Die perfekte Vorbereitung auf das Case-Interview in der Unternehmensberatung 
CoachingPlus 5 
