Hi, I did English Lit + Lang at A Level. Grades at GCSE seldom translate into ability at A Level because different qualifications are looking for different things. It's common for people to do very well at GCSE but flunk A Level because they aren't able to make the jump. Whether or not you succeed in A Level English Lit won't entirely depend on what you got at GCSE, but rather:
1) How you study.
2) Your analytical skills.
3) Your exam technique.
4) The amount of effort you put in.
Notice how all four of these things are in your control. And you're not competing with people in your class. This isn't like GCSE where you're in constant comparison with each other - in A Level, you do more work independently. The only person you're competing against is yourself to be better and better every day. And if you follow the four things above, you will. I would definitely recommend taking English Lit if you're passionate - it's not an impossible A Level by any means and you can get an A if you put in the effort.