Typically you'd do a GCSE in English Language and a GCSE in English Literature and if you got an A in one, it has no baring on your mark for the other one. They are two separate qualifications.
so does that mean u need to get at least a C in both of them
They're SEPERATE GCSEs however GCSE English Language is the more important one as if you fail e.g. get a grade D you'll have to resit it in year 12 whereas GCSE English Literature, if you fail, you fail! When colleges, employers etc. ask for A*-C including English and Maths, they mean the English Language,
It's only English Language which you need to get a C in or you'll have to resit it.
You can think, GCSE English Literature is a bonus GCSE.
Hope that makes sense.