Not sure about all of their qualifications, but Best Athletics aren't shy of taking on people with very complex issues that inform their running. One of the coaches (I think it's Sam but I'm not totally sure) has an athlete with them who has severe mental health problems, some of them correlated to an eating disorder, and a history of chronic overtraining that makes Sarah Fit look positively lazy, running through stress fractures and worse.
It concerns me that they're willing to coach someone like that without the appropriate skills to do so. If they are certified in the correct way and I've somehow missed it then fine, but the ethics of, in some ways, endorsing disordered behaviour by reinforcing a high level of training when rest would be more constructive are fuzzy at best. I sincerely hope they aren't just willing to take on anyone and everyone willing to pay them, so long as they're going to run fast times.
It's really struck me recently with all the posts about marathon recovery and how much time the body needs to recuperate just how many insta runners do not give themselves adequate time off. A week off running? No chance - they're back at it within 48 hours. Still seem to get away with it without an injury though.