I would argue that medical students already are forced to work in the NHS when they qualify. If you want to train and get to consultant level, there are literally no other options, it’s a monopoly employer. You might be able to go and work in Australia for a couple of years, but it’s really hard for UK graduates to enter specialty training over there, so if you want to train and progress it’s going to be within the NHS, for far less than those skills are worth on an open market, I would add. It’s already pretty much indentured servitude.
Plus, as you point out yourself, medical students pay the same fees as everyone. The difference is the degree is longer, which is exacerbated if you do graduate entry medicine. Then, especially in the clinical years, the placement hours are so
long and the exams so intense, that working a part-time job is almost impossible. This means that, unless you’ve got pretty robust parental financial support behind you, by the time you graduate you are at a financial disadvantage compared to other people who studied other, shorter degrees, who will have less student debt and likely already have a year or two or three of working behind them.
Then you graduate into a system where you apply nationally for a job, and competition is fierce. Already every year there are hundreds of final year students on the waiting list for foundation jobs. You can also be sent anywhere in the country, and if you turn down the job (say, because you don’t want to move away from all your family and friends and support network) then you will just not have a job. Which is an issue because a newly qualified doctor is literally not allowed to work outside the NHS foundation programme, you have to complete the first year to gain your full license to practice, there are no other options.
Medicine is already a career where those from privileged backgrounds are over-represented. Raising the fees medical students pay or forcing doctors to work for a certain amount of time in the NHS with the threat of having to repay their university fees hanging over their head would only make access to medicine harder for those from working class backgrounds.