it depends in my opinion (and this is only my opinion), on the circumstances you failed. I'd recommend talking to your teachers about how you are doing after your next set of mocks, they may well improve your predicted grades based on improved scores in your mocks and also you coming to them and showing you have a desire to work hard and improve. its difficult to say what your predicted grades are as you are in Y12, if you got Es across the board and suddenly got As across the board in your next set of mocks they might either boost you up to a B or something or stay more around a C. Talk to your teachers is your best chance of getting your predicted grades where you want them.