Yes, unfortunately it will affect your chances, anything less than straight A will be a negative factor when your application is being weighed up and most medical schools want at least eight GCSEs. On a positive note you will have A in maths and science: is there any way you can work them up to A* and an A in English?
I have myself had to consider how GCSE will affect my medical application and I have *****AABBB. My five A* are in core subjects though (E/M/S plus English Lit and Statistics); despite not having as many as I liked and being disappointed with three B grades, I decided it was acceptable with a well-written PS and AAA AS level grades. It did mean Birmingham was out.
I am in college now with several people who wanted to read medicine last year or after leaving school, but they realised their GCSE and/or AS grades would make it almost impossible to get an interview. If you cannot do better than a mix of A and B and only have so few GCSEs, and still have your heart fully set on M, you may consider going for an ordinary science degree then graduate entry when you have more academic experience behind you. You may also consider pharmacy or nursing if your main reason for medicine is to help people in need etc. and these are far more open to people with good A levels but not so good GCSE scores; another one popular with those who have found the medicine degree is beyond them is Psychology, a wonderfully captivating subject and a path to very rewarding careers.
Above all, be realistic. What are your career plans after med school? Do you intend on going into academic med/ research afterwards? If so, life science degrees can lead to many of the same ends. Don't put yourself down but equally don't set yourself up for a fail.
Do you go to a school where SMT are obsessed with league tables or new fads? Were you coerced or forced into doing the Diploma on promises of it being worth numerous GCSEs? That sounds like a good thing to protest against if so, as many people appear to be in the same situation this year: disadvantaged on University applications because of a decision made by their school when they were 14.
As a comprehensive pupil myself I was led to believe BTEC was better for options subjects than GCSE because it was "worth four times as much"; the fairly transparent ulterior motive being to boost their rock-bottom League Tables standing. Pupils in the bottom five of the nine sets for sciences were required to take a level two BTEC in applied science. They would have only been entered for Foundation Tier in any case but that system constitutes a violation of their right to take the better respected qualification.