Hello! East Midlander here. I began seeking my ADHD diagnosis from the NHS through school at 14. I am now 18 and still have not received a diagnosis yet. I would absolutely NOT recommend NHS services for pursuing a diagnosis particularly if you aren't old enough for adult services but also arent a young child- or a female because they are statistically proven to be more often misdiagnosed or not seen as "having it bad enough" so to speak. If you can afford to access the diagnosis privately I would 1000% push you in that direction. If you must use the NHS you will need to be prepared for long waits, patronising GPs and a LOT of fighting your own corner.