I'd go with the one you enjoy most. I know that's probably not making this any easier, but at A Level, enjoying a subject can make a significant difference. You can be pretty decent at a subject, but enthusiasm is what makes the real difference.
History - I'm not entirely sure if the exams at A Level are source-based, but my friends do the subject and they really enjoy it. Quite a few of them did it alongside science subjects last year too, one of my closest friends did History alongside Chemistry, Physics and Maths. The workload is pretty big but it's still manageable. Most schools (ask your school's History department for their entry requirements) only need a B grade at GCSE, so you've still got from now until next May/June to bring your grade up. If sources are your weakness, practice makes perfect. Ask your teacher for tips on how to tackle the sources, and ensure that your essay writing is up to the highest calibre so that if you fall back in the sources exam, you can make up for it in the essay exam and your grade will balance out.
History works well in combination with Religious Studies, although I suppose to some extent, you could argue English works well with RS too. Both History and English Literature are considered facilitating subjects.
English Literature - Again, the workload is pretty huge, but I'm sure this comes as no surprise as you've probably already been warned of the 'big jump up from GCSE'. There's only 3 people doing English Literature at my school, one of which I'm pretty good friends with. We've never really talked about it but I know it's far from his favourite A Level. I'd recommend having a look at the set texts before you make the leap to choose English Literature, just in case they change year on year. The depth of analysis is a lot deeper at AS/A2 as well.