There's definitely a chance. Some universities place a lot of emphasis on GCSEs so you will have to do some research into which med schools require which GCSEs. Some have a minimum standard you have to match, and then they are never looked at again, others have a minimum standard but then give preference to higher numbers of A*s later on in the application process.
Remember you will also have to get work eperience, UKCAT and be able to write about ways you've demonstrated certain skills (communication, leadership etc) in your life (hobbies, jobs etc).
Good luck with whatever you decide.