There are a variety of options for altering and changing buildings and properties which do not require planning permission, these are known as Permitted Development Rights. In order to establish whether planning permission is required, you need to apply for a decision as to whether Prior Approval is required.
In this case in Henley-on-Thames, the owners wish to keep the frontage on the street for commercial use which is what it was designed for but convert the remainder of the ground floor and upper floors into flats. This is a very welcome alternative as it gives the opportunity to maintain an active street frontage for Henley but also introduces living accommodation bringing life into the town and also adding to the security of the property. In this case, Prior Approval has been deemed not to be required, which means the owners can press on without further planning permission