as far as im aware AS exams do not carry nearly as much weight as they used to. it might be specific to your course, but i highly doubt that they will even impact your final grade.
your teachers at college are there to help you. ask them for support for coursework, there are always late entries and editions each school sends off with a batch of coursework. you have way more time than you think.
i applied for uni about two weeks before the deadline, got my pers. statement sent back to me, and it was sent off about 3 days before the deadline. i received offers from all 5 unis in two weeks.
im proof u dont need oodles of time to get on the path to succeed!!
you have the whole of y13 to get on track. i think they will accept you back. it will be like u never said you were leaving in the first place!!