We used to use the two following companies
and
Melissa who used to work for The Talking house has her own company now
the best way to find SLT in my view is via the website https://asltip.com/find-a-speech-therapist/
Basically you put in where you live, and what sort of SALT you are looking for and then it produces a list of SALT within a certain distance. I just then wrote a generic email , telling them about my child and what we were looking for, for example we were looking for a therapist who could travel to our home and could do oro-motor programme etc. I think I emailed 10 and 3 replied of which we selected one that was the right fit.
I don’t have experience of the below but I found them via a search
https://sltleeds.co.uk/who-and-where/
bluebellsupport.co.uk