The flight school you’re from is important to some companies, but Ryanair absolutely is not one of them. The RYR Mentored program always felt like a waste of money to me.
They appear to not really care that much, about where you did your training etc. I’ve seen plenty of people get invited for their assessment. Ranging from the most obscure and unknown flightschools, to having done their training at 10 different places, you name it.
Don’t overthink it, get a cplmeir with a flightschool where you’re comfortable.
IMO; Where it gets important for successfull airline assessments; a good MCC and a sim prep for the specific assessment profile. That’s what’s being judges in the end.
Also, don’t hyperfocus on technical skills and knowledge. The non technical part of the interview is equally important. Show that you can be a good coworker.
After a few hrs almost everybody will be able to fly the operation, but not everybody will be able to be a good coworker.