Cs are thought to be passes - On most universities they usually say "at least C in..." you'll be fine with Cs as they are passes. And an Access to Humanities should be good ( I think? ) for it too surely
I got into Cambridge with just average GCSE grades like C's. As long as you can give a good reason (even such as lack of direction/motivation when you did them!) and show you have academic potential, you've got every chance of getting in if you do an Access course (or equivalent)