I only used 2 months to prepare for my grade 7 piano exams and i failed the first one but passed the 2nd one. I almost never worked on the oral part but concentrated on the 3 pieces and scales. My result is 11x i couldn't remember and I failed the oral part ( not too low the marks, i guess it was becoz the examiner adjusted the mark for the part so to make it not so big'difference' from the rest of the exam.
Scale -- you dun need to play really fast to get good marks. As i was qutie nervous at the time of the exam , I played slowly but the result was still good ( 18 marks). Normal practice shall be fine.