I think it depends on the local authority. Not all of them demand three separate sinks, for example. I don't think they had different ratings when I ran my business (I closed it in 2015) - it was just a question of whether you could display the certificate or not. A fail didn't mean you had to be shut down. When the inspector visited it was always unannounced, and there was a kind of hushed atmosphere while she put on her white coat and started checking in the corners and inspecting the fridges. The visits always seemed to be on hot summer days. But she never found flies or cockroaches or out-of-date stock - it was always about bureaucracy and ticking boxes.