Reality of university acceptance for Medicine? Mature student

Im a mature student at 23 years of age. I'm currently studying Access to Nursing and since realised I would like to further the course after its finished into Medicine. I'm enrolling on an Access to Medicine course next year (2017) My approach to study has changed a great deal and have already achieved two distinctions.

I've been looking at KCL, St Georges, Brighton and Sussex and Southampton.
My worry is that I didn't do brilliantly in GCSE, I received a few B's and C's including a B in Maths. I am planning on retaking my English GCSE alongside the Access course. I understand lots of unis ask for As/Bs in GCSE

I also did A levels and recieved two D's in English Lit and Art

-I'm extremely hard working and dedicated to the course and aim to achieve the distinction criteria. Previously had no targets in school but have since changed how i approach education.
-I am undergoing volunteer work within the NHS on the maternity ward and within a student volunteer programme.
-I plan on achieving a certificate in British Sign Language next year.
-I will be taking both the UKCAT and BMAT.
-I have worked within a customer and people based career for the last 5 years

I would like to know if realistically any uni would accept my application?
Also how important are GCSE's within the Uni Application process? / How much do they count for?

Any Suggestions?

Thanks