I have to say in regards to princes trust, I agree with you in that their specialist areas are poor, im in the film industry and i have to look at other sources for support with filming but with the business side of things they are great. My mentor has no clue about filming but helps me with all the business aspect, they've saved me a lot of money as well. I believe you can get what you want out of them, they wont chase you but they will support you if you ask for, if you are not happy with your mentor they can change the mentor they have always said that and they also say it is up to you and your mentor where you meet, and it can be at your location. They have lots of small courses to help develop basic business skills.
If specialist help in creative industries is what you want then i agree go elsewhere but if you want support getting off your feet, they are great.