You'd end up with 2 additional GCSEs. You won't have repeated double-award Science, but will have additionally taken single-award Chemistry and single-award Biology.
Note that the single-award Chemistry and Biology will contain more content than you'll have already covered in double-award Science, so expect to be learning new topics, not just recovering topics you already know.
It's also worth checking if the exam board is the same as the one you used for double-award Science. If it's different, be prepared for differences in the way questions are asked, and potentially how marks are awarded.