I do feel his pain. My son was in the same position. He was 18 years old, an excellent sportsman doing well in his sport playing in National Championship finals when he got excruciating pain down his leg. We paid for a private physio because he was in such pain. She said it was muscular. Having suffered from similar at the age of 16, I was disbelieving so I insisted we paid for an MRI. It was literally an act of desperation in order to get the GP to refer.
The MRI showed a prolapsed disc so we were referred by the NHS for a spinal block. This worked for a short time before pain started up again so after about a year, he had another. Once again, he had a short period of relief before the pain came back. The GP wouldn't refer him to an orthopaedic surgeon until he had another MRI so we paid for another. The prolapse was worse so he was referred but had to wait for a long time before he got an appointment to see the consultant. Unfortunately, the waiting list for an op was at least 12 months and Covid put it back further. We researched private ops (about £8000) and, as his NHS consultant worked in the private sector too, we went down to see him on the NHS. We explained that any op on the NHS would take him into his finals at Uni, his congenital condition was getting worse with a lack of mobility and the consultant persuaded us to leave the private option and he would do what he could to move him up the list.
Last week, 6 months after that appointment my son had his discectomy and he is now in a much better position regarding pain. His was a large prolapse which never got any better but we were informed that the reason they don't operate quickly is because for most, the recover time without surgical intervention is 18 months so you may not want to go the surgery route immediately. Perhaps you should research spinal blocks (I seem to remember that it was about £1000-£1500) for the first injection and MRI.