So I was diagnosed roughly 10 years ago as an adult. I was on 2 waiting lists of two different clinics. Queue times used to be between a year and 18 months at the time. I also told them I can take any appointment that may open up spontaneously. They just have to give me a call and I‘m there.
Luckily a spot did open up so I only waited for around 6 months overall. I got lucky. Nowadays a lot of people want to get tested and everything is clogged up.