The l4/5 disc is narrowed with a central disc hernia with severe bilateral lateral recess stenosis what is the treatment for this please?

Depends. If pain is mostly down the leg (s), an epidural steroid injection could help....Surgery last resort. If its just low back pain, then physical therapy, with surgery as last resort.
Maybe surgery. Depending on the severity of the stenosis and your symptoms, surgery, or possibly steroid injection, would be the likely treatment if you have already gone through physical therapy, which should always be part of any disc treatment. Get a referral to physiotherapy, if not yet done, by seeing your gp and discussing the treatment plan. If beyond that, see gp or physiatry for surgical referral.