Many medical schools give each applicant a score and many use GCSE results. That way they can shorten their very long list of candidates! Don't give up though. Also, as a last resort, you could even apply to a Biochemistry course or Genetics or Neuroscience and after the three/four years you could apply to Graduate entry Medicine courses. Many people do this, I know a handful of people that have done this and in most cases, some of the modules in their Medicine course they have already studied in their previous course, which has been very advantageous of course!
I did a work experience placement over the summer holidays and a doctor told me that although academic brilliance is necessary, you need so much more than that to make it as a good doctor. Please remember that.
Med-link will be a great way for you to make your application stand out and I'm sure someone there will be able to give you some great advice concerning your GCSEs and applying to Med-schools.
My advice: Don't give up, persevere and if you want to become doctor, then you probably will become one. However, think long and hard about WHY you want to become a doctor before committing to a life of being one. (Also, that's probably going to be a question in your Med-school interview.)
If you need any more help/advice, please do not hesitate to ask me.