You are a wonderful grandma by reaching out and being proactive! There’s so much help out there! I’ve never personally dealt with Schizophrenia, but have with other mental health issues (I’m 62). I live in America, and when I pour over picking a Psychiatrist, I am noticing more and more that they include Schizophrenia as conditions they work with. When they literally list it, that gives it a lot of weight! Isn’t that encouraging?!?! They’ve come so far regarding the various mental health conditions!
If it were me, I’d start with finding a Psychiatrist who lists Schizophrenia out in the open on their website as conditions they treat, then after finding 2-3 of those, I’d call their office and get further information on how much they’ve dealt with it, and what types of testing do they do.
Another thing I would do is look up as much as I could about the illness, so you’re armed with knowledge! That can be (here in the USA) Mayo Clinic, Johns Hopkins, WebMD, Stanford studies on Schizophrenia, or similar high level places in the UK. I’ll be one of your cheerleaders 📣!!!