start drafting your ps now, so long as your doing a little everyday and doing revision consistently youll be in a much better position.
some people get offers the next day and some will get it very late, once youve submitted ucas try to push it to the back of your head, take the descisions from the uni as they come, no point in stressing about offers when it's beyond your control when the admissions teams go through your application
it's your final year of school! enjoy it! enjoy the friendships, lessons, lunchtimes and leavers assemblies
so long as you have a revision schedule and your stick to it youlll be well prepared for april/ march when youll start stepping up to more practice papers
good luck!