To get your grades up, well the solution is quite simply really; revise. I know that the thought of it is horrible, and by revising you dont just have to sit and stare into dull books, make it fun! My English literature notes were quite colourful, and my coursework helped too. There are plenty of websites which could help you with revision material on the subjects that you are predicted to fail, but as emiloujess said don't trust the predicted grades. My predications were lower than what I actually got.