Which college for A level in Manchester is the best one for study Medicine

Hi guys, I'm confused about choosing Aquinas College, Xaverian College or Loreto College to study Medicine after finishing A level.
Do you guys have any request about which college is better for after finish A level study Medicine? Aquinas is a good college for science? How it is Xaverian or Loreto?
Another thing, while studying for my A-levels, can I start working in the medical field, such as a doctor's assistant, shadowing a doctor, or doing voluntary work? Or is this only possible after finishing my A-levels?
Do I need any prior experience to work or volunteer in the medical field while studying for my A-levels, are there any colleges that offer medical placements or work experience opportunities for students?
Thank you!