As you say, it's a great opportunity for you to be able to give your experiences as a service-user and potentially help improve the services for many other people.
Remember that being psychotic is in no way a failing on your part - it's just a part of your illness and it happens. As a professional, your old psychologist will understand that, and they will also understand that it isn't
their fault that you have these symptoms, so whilst they understandably won't feel happy that you're ill, it's nothing that you have to protect them from.