Ah, that makes sense why people feel so strongly about advocating for self-diagnosis. It also makes sense why some people are really concerned that they weren't autistic enough at their assessments because re-evaluation could be near impossible. That's such a disservice to the autistic community. What do they expect people to do while they wait for assessment? It's not like people are doing great and think, "Maybe all my success is because I'm autistic." If this comes up, there are probably some considerable difficulties going on for someone to consider they're autistic. I was not aware of that and sorry you're in that situation. Thank you for sharing.
If you have the energy to endure the process, it might still be a good idea to get on the wait-list. Three years are going to go by whether you're on it or not. However, I could see being pretty distraught should the GP be invalidating by denying a referral and potentially having that in your national medical record. Another idea would be to maybe find a way to save up little by little to see a private provider, even if it takes a few years.
BTW, I want to be clear that I'm thinking of ways you could get assessed only because the diagnosis was very helpful for me to make sense of things and access proper autism services.