I have recently been thorugh some of the debates on the Act. There were several amendments proposed for a "small events" exemption, but they were always defeated, sometimes because the case for them was not accepted and sometimes because they were technically inappropriate (i.e. badly written). In the end the "small premises" exception was written into the Act, primarily on the basis that small premises can only host small events but in large premises you cannot know whether an event will be large or small until the audience arrives.

Richard