No, they're not all like that. I've used two schools for self-fly hire, and while neither were perfect in all ways, I've not had problems like you describe - or rarely. One had fantastic availability, and I could often get a helicopter for a longish period at a day or two's notice, if I decided suddenly to go to a fly-in or something like that. I don't know where you're based, but if you send me a pm I'll be happy to tell you who they are.