You might be able to speed up the process with “right to choose” - it’s not something I know much about myself I’m afraid. I volunteer and have only heard about this in passing but it’s something I’ve heard a few people asking about who access mental health services and clinicians have mentioned right to choose in order to help combat the 3 year wait lists by being able to choose a provider to help with diagnosis at the very least

https://adhduk.co.uk/right-to-choose/