If the course isn't too over-subscribed, they would probably allow a C. I have the same problem with Creative Writing and my Firm wanting a C in English Literature, which would be impossible as i've mucked up two major units.
What grade do Bath Spa want in English? If they want a B as well, you might have to go through clearing if you get a C, but if you get ABC and they only want BDD, it's pretty likely they'll let you in anyway. As for Kent, it depends how many people accepted their offer and how many others missed the grades, but it's definitely possible they'll let you in anyway. In the meantime, work hard and try and get the B!
Kent are usually pretty good with accepting people who drop a grade - I know a girl who got on to a course requiring ABB with CCD! Granted this was based on a different department and course (Computing) but Computer Science at Kent is still pretty popular. I heard similar stories from those on other courses too, although not usually as extreme!