Retaking A levels in NS

Does anybody know how retaking A levels as a private candidate work while in NS? Lets say i down pes to a 9 to 5, how do i take the exams in November though? Would i need to take leave to go for my exam?- but here is the thing, i will only have 8 leaves left after the upcoming block leave. Given that i take 3H2 and GP, that would minimally require 9 days to take the exam.

So here is my question, are you able to go for your exam then come back to work overtime? Or do they give u chance and just go for the exam and come back without needing to use your leaves?

Please let me know, thank you guys