The rules say that you're contractually obliged to take up the CI place if you meet the conditions and are rejected by your CF choice. But you can try contacting your CF, or go into Adjustment/Clearing. Your CI university will likely release you if asked, because they don't want to admit unhappy students. Bear in mind that if you don't reach the entry requirements of your firm, your chosen university won't automatically reject you. They'll have decided to, so will unlikely be willing to consider you. You shouldn't worry about results day at this stage. You might get the grades needed, or your CF university might accept you if you narrowly miss the offer. Find out more about replying to offers.