Although volunteering on the wards and your work in the lab is good, do you actually have any work experience that has helped you understand being a doctor, rather than just hospital life in general? I think that would be a good idea, especially if you have to explain why you chose medicine and not nursing.
Not direct work experience, I'm not sure what you mean? I communicate with doctors regularly to give results and work alongside them in the lab, but I have never performed work outside of my responsibility.
I mean where you shadow doctors on the wards/in clinic doing their usual job. The lab environment is usually fairly removed from the chaos of the wards, so it might be useful to get out there and find out what doctors who aren't in the labs do on a daily basis.
Thanks, aside from experience, any idea if I'd be eligible
Your situation is somewhat unusual, so you should check very carefully with each university you're considering applying to whether your GCSEs would be ok and whether your Access qualification would be accepted. If they say they're alright, then yes, you definitely stand a chance!