I went to my GP and she basically said that the waiting list is too long and she can refer me to any of theese places(link below). I don't really know what to choose, if you live in the UK please help me
https://adhduk.co.uk/right-to-choose/
I went through Psychiatry UK for mine and they were fine, although from your link it seems they are currently one of the longer waiting lists, so I would suggest trying someone else with decent reviews. I didn't need to wait long (maybe a week) for my referral to be confirmed, unlike the other person in this thread.
I would suggest making sure that the provider is a yes on the "Authorised to provide NHS ADHD Medication Prescriptions". You can sign up for an NHS pre-pay certificate once you are getting regular prescriptions to save on the prescription payment.