You can’t conclude that 8 GCSEs is not enough from that graph, @OctogenarianDecathlete. The only useful information you can take from it is possible to be accepted to study medicine at Oxford with 8 GCSEs. You would need to know more information to ascertain whether having less GCSEs was detrimental eg did the applicants with less GCSEs have lower UCAT scores.
I posted the link because it clearly explains the process. Oxford selects candidates for interview by ranking them using their GCSE grades and UCAT score. They look at the proportion of 8/9 grades a student has. They also take into account how a student has performed relative to other students at their school so applicants from poorly performing schools are not disadvantaged. They also look at all the applicants who have not been selected for interview to see if there is any reason why the algorithm they use might not be a good predictor of their academic potential eg poor GCSE grades due to illness or technical issues during the UCAT test. A student who has 8 GCSEs who attended a school where that is the maximum number of GCSEs should not be penalised because there are measures in place to prevent that.
It also gives the criteria that interviewers are supposed to assess at interview. Number of GCSEs is not one of them. Nor extra curricular activities nor work experience. What they should be assessing is whether the applicant shows academic potential from their answers to questions, whether they have insight into the skills and traits needed to be a good doctor and can illustrate that they have those abilities from what work experience they do have, whether that comes from reading medical journals and a Saturday job at Aldi or mummy and daddy paid for a 4 week trip to do work experience in a hospital in Soweto.
Some medical schools don’t even look at GCSEs. You should be able to find similar information to the link I posted for other universities somewhere online.
The medical schools council has useful up to date information on work experience and GCSE requirements. You will probably have to go to the universities own sites or look at FOI requests for more detailed data and information on their selection criteria though.
TBF probably would have given similar out of date advice if I hadn’t been through the whole med school and Oxbridge application experience more recently as a parent. FWIW one of my DC did lots of outreach work and applying to medical school talks as a medical student.