Roger - I see where you're coming from, and they can of course impose conditions. However, it is clearly the case that these conditions do not have 'effect' with regard to live acoustic music if, as section 177 subsection (4) states, the premises license is for 200 people or less and that license includes the provision of music, and if it's between the hours of 08:00 and 24:00.
John Barden