Got my assessment tomorrow and I'm nervous - could anyone give me an idea of what to expect?

Hi all,

I'm a 31 year old woman. I was diagnosed with ADHD last year through Right to Choose and it was recommended that I also go for an autism assessment. I got a very last minute appointment booked today with PsychiatryUK after being on the waiting list for a couple of months because I've been wanting to get any potential diagnoses over with ASAP. If I do have autism or if I don't, either way I can begin looking at my life and dealing with things through the very new lens of being neurodivergent. However, now it's booked for tomorrow and I'm terrified. I can't help thinking that they're going to tell me I'm wasting their time as I already have an ADHD diagnosis. I was told by a psychologist a few years ago that 'if you have ADHD, you'd probably meet the diagnostic criteria for autism too so don't bother going for both assessments'. I think AuDHD would explain a lot of things I experience(d) that falls outside of the ADHD diagnosis (extreme aversions to certain sensory input and childhood hyperlexia, for instance) but I'm also half-convinced that I'm a fraud.

I think the issue is not knowing what on earth to expect! The anxiety of speaking to new people, who are going to examine me and my childhood to find something 'wrong' with me, is overwhelming. Not that I think that autistic people are wrong - just me, if I am. I've been googling away about the kind of things to expect but I'm struggling to get a grasp on it, if that makes sense. It seems like a very short appointment for such a complex diagnosis, especially for people with other conditions that overlap, and I'm worried about an inaccurate result either way. Like I said, I'm also worried that I'm wasting limited time and resources that could benefit another person more than me.

Essentially the spiral is real right now and I think it would be really helpful to get an idea of what's going to happen so I know how to behave!