Your voluntary work sounds good, quality is better than quantity so as long as you can reflect on these placements reasonably then you'll be fine.
What I highlighted in bold above is a bad answer for wanting to study medicine.
I'm not trying to bust your ass but they will pick up on this and hound you, it's all well and good wanting to help people, but there are a lot of careers that do that.
Firstly they will probably say something like '
You want to help people? Why not become a fireman? Or a nurse? They help people'
Secondly they will question your dedication to medicine, '
why did you feel it was necessary to pursue a career in genetics? We understand that some people do not decide to do medicine until later on in their life, but what made you change your mind?'
How do you not know your GCSE grades? They will ask for these on the UCAS form surely, and the admissions will want to know the grades you got for certain subjects, for example Maths, English Language and the Sciences. GCSEs are the first hurdle in a medical application, if you can't provide information on them your application is already seriously lacking. Find out what they were.
Are you aware of what the UKCAT is? Do you realise that if you drop out of your course for medicine you are not guaranteed to get a place in medicine?Please answer the questions in bold, thank you.
As for giving them your 1st year grades, email/call the specific universities you plan on applying to and ask them?
Another question,
what universities are you planning on applying to?