Starting 6th Form and Want to maintain a good academic and social life

So, I'm starting 6th form soon and i done quite well at GCSE i got 7 A's, (might remark english to get an A* as i was one mark off) a B, and C.
I got accepted into a grammar school and so far I'm overwhelmed by everybody i see. Their either good at sport, have good grades or are a mixture of the two.
I have to do a language GCSE; Spanish, during my AS-levels as I want to apply to an Irish university and that is a general requirement (it also just looks good for university applications).
I'm also hoping to repeat Biology, Chemistry, Physics as i got a 7, 7, 8 and i know i can do better (I got really ill twice over my exams, specifically the first and second science exams) and it would just help to spruce up my university applications.
On top of this I've chosen Biology, Chemistry, Physics and English Literature (might change this to math's as i got an A in both of them and quite enjoyed them) and I'm aiming to get A*'s in my chosen A-levels as that is what's aimed for at my new school. My school has already stated that we must do at a bare minimum of 2 hours of revision each day (I believe excluding homework).
I've also got to do a minimum of 150 hours of volunteering at a hospital (it is to get a golden certificate to show universities) and i intend to ask my school to help me get work experience in a clinical setting or ask to shadow a GP, and plan on getting a job (all preferably close to my school).
On top of this I've got to take an active part in extra-curricular activities (my school also placed a large emphasis on these - I'm quite good at art, writing and can play the drums) and make my face known to teachers as i want to become head boy and this is made harder by the fact that most other kids at my school didn't enter this 6th form and had started since 1st year.
The question I'm asking is how do I balance the GCSE's I plan to re-sit and take alongside A-levels, alongside extracurricular activities, alongside a social life, alongside driving lessons and a job. I don't want these next 2 years to be a misery and I'm looking for general advice and maybe some tips and tricks.

I've always been at a grammar skl and for head boy/girl they don't really care if uve been a previous student or not. Maybe some ppl/teachers may have a bit of bias but if u prove urself and show u know their ethos and aims and what values they want to instill in the students ur good to go good luck.
Btw how did u get that experinece? (150hours) How did u apply? Where was it if u don't mind me askinf

thanks for that bit of advice (i know at some schools head boy/head girl can be a popularity contest) it really helped!!!
in regards to my volunteering, im from northern ireland, so i have to go to my local health trusts website where they have an email for me to send my local area (so they could assign me to a hospital) and request an "interest in application for volunteering form". So i filled that out and im waiting for some teachers to be my references but its hard because i just recently moved schools. They got back to me pretty quickly tho!