Good Lawyer Guide's response

The commercial use of all property must have authorisation of some sort from the local planning authority. The law sets out what planning authorisation is required and, when a change of use is proposed, an application must sometimes be submitted to the planning authority.

But where the change of use is within a specific category, explicit authority from the planning department is not required – authority is implied by law. This includes uses within the B1 class which includes offices not open to the public, research and light industry, for example. So long as your business is within the B1 class you should not need to apply to the planning authority to carry on your business. If you have any doubts, speak to your local planning office.