Sleep is very important. You may not feel like you need sleep, but trust me when I say that research greatly disagrees with that. It's best to sleep plenty, 7 hours is good, maybe you need more at the age. However, you shouldn't bother too much if you're working hard all day and not cutting sleep as a result of procrastination, then it should be a battle against fixing that procrastination. Maybe I'm talented, but I'm very sure that if I devoted my study during the day and not rushing in the night, by GCSEs would be primarily A*s. Not that I have hindsight, GCSEs aren't really that hard. I managed to get A-A* in most subjects from just revising the day before or on the day. I'm reading books and you should too to help improve that aspect of you. I recommend "a mind for numbers" as a read, you should really invest that money and read it while you still can. But, overall there is plenty of time during the day to revise. From experience, I would say that most times you cut into sleep time is due to you wasting time during the day. Especially when you get to late year 11 when you primarily do private revision. You should really fix that now, if you feel as if you have a problem with procrastination.
Edit: the book "a mind for numbers" covers plenty of aspects on procrastination and you as a student. All memory skills and learning tips can be applied outside of maths/sciences.