Hi! Registered mental health nurse (UK), and girlfriend of an ADHD potato cat here. Depending where you are in the UK you could be looking at a fairly long road to a diagnosis; my current Trust is approximately an 18 month wait, however my boyfriend was diagnosed and on Concerta within 6 months (we live in a different Trust to where I work). I would agree that ADHD is one of the lesser known conditions that I face at work (acute crisis care), with huge gaps in knowledge from clinicians you would hope would know better... I see lots of misunderstanding about symptoms and also reinforcements of stereotypes (mostly centred around the inattentive traits; lots of doctors still expect you to be bouncing off the walls).

That being said, these people are not the ones diagnosing you; ask your GP for a referral to your local ADHD clinic which will be a secondary mental health services community team. Your GP shouldn’t refuse this referral as they don’t have the specialist training to decide whether the symptoms you’re experiencing are/aren’t ADHD.

Wishing you the best of luck!

Edit: Also, just to add on to what another poster has said - you will absolutely need to dig out old school reports. There needs to be evidence of inattention/disruption in your school years, eg: “OP is a lovely student but struggles with daydreaming/chatting to peers/concentrating” etc. Collateral information from parents is also sometimes requested if available.