Yea see chemistry was never a subject i liked, i admire your courage to pick it. Theres always space and time for improvement, i tell myself that everyday, so even if you do not get the grades you desire or have surpassed your expectations i suggest use "save my exams" if you really wish to invest in anything invest in that. Make flashcards online/whatever way helps as they follow the specification of each exam board thouroughly. Trust me when i say it helps, i use it and it sorts out past paper questions on each topic with the level of difficulty you wish to do. So this summer it may be something you wish to consider doing. Good luck, i hope all goes well