Not all uses fall within these classes and are regarded as sui generis (i.e. "in a class of their own"). Changes of use falling within classes do not usually require express planning permission nor planning applications.
Changes between classes often do require planning permission. The Town and Country Planning (General Permitted Development) Order 1995 Schedule 2, Part 3 sets out circumstances in which a planning application is not necessary, but if you are in any doubt please contact us for advice before proceeding.
There is a booklet entitled "Planning Permission - A Guide for Business" available from the Planning Office which includes helpful advice as a guide to the planning system for businesses. This document can be downloaded from the Communities and Local Government website from the link in the external links box.