My son was diagnosed in Leicester at the Nuffield Health private hospital. He saw a very experienced consultant there who diagnosed him over 4 appointments, (aged 15) and prescribed his meds. After 2 months this was transferred to my local GP surgery and we then got them on the NHS monthly.
Son no longer takes the meds, but they were invaluable to get him through GCSEs. He uses his ADHD and especially his hyperfocus to his advantage now and although his room is a tip, he loses his wallet and phone all the time, is always late etc, he says he would NOT choose to get rid of it if he could.
A few weeks ago he took one small dose of his meds (we still have them in our safe) to do his Theory Test and said on the way back how dull it must be to be "normal" and have your brain just think one thing at a time. :-)
Interestingly, the consultant at his diagnosis asked him, "which of your parents was in trouble at school", and he said "Mum". After a chat about my history, the consultant said the likelihood of me having undiagnosed ADHD was extremely high as well, and it was a lightbulb moment for me!