On TSR I've seen quite a lot of people with weak/no A-levels and below average GCSEs asking if any medical school would accept them. They seem to assume that their only problem is getting in, and once they get there they will be fine. It's much rarer to get someone with a weak academic record wondering if they could manage the degree itself, and to be honest, I think that's one of two main questions you need to be asking yourself here. Graduating with a third in your nursing degree suggests that you found the academic side of it a struggle. Realistically, what are you expecting to be different about medicine? Graduate entry medicine is particularly intense, because all the teaching has been condensed into a shorter time frame. Rather than asking universities if they will waive their entry requirements, you need to be thinking if and how you would cope with that.
The second big question you need to ask yourself is why you want to do medicine. Even if you had a perfect academic record, telling GEM interviewers that you're applying because you've "realised you could do more to help people" would be a certain way to get rejected. All healthcare jobs involve helping people, and there is no hierarchy of helpfulness. I think you're making the mistake of assuming that the more intellectually difficult something is, the more morally/socially worthwhile it must be, and this isn't the case. Thinking about it from a patient perspective, one of my most unpleasant hospital memories is temporarily losing continence and having to be cleaned up by the HCA. Hardly the most glamorous job, but an essential one, and that person sticks out in my memory because she was kind to me at a time when I felt terrible. So "wanting to help people more" isn't a sound reason to pursue medicine on its own. Wanting to understand physiological processes in depth and to critically apply this understanding to problems that can be very nebulous and fast-changing would be a better reason, but this brings you back to the academic requirements, and whether an intense four-year course with heavy science content would bring out the best in you.
To be honest it sounds from your post that you're romanticising medicine, perhaps because you've taught yourself to see nursing as second best when it's just a different job. In your situation I'd be looking around at the various roles and specialisations that exist within nursing, and thinking about how you'd like to progress there. If your idea of yourself as a nurse is "not good enough to be a doctor", you're setting yourself up to feel unhappy and inadequate in your career, but you can create a positive identity for yourself in nursing that's all about what you can do and what you enjoy doing.