Whether you need planning permission or not will depend on the build. Orangeries are considered single storey extensions and follow the same building regulations.
If you build within permitted development regulations, planning permission is not necessary. We can advise you on the parameters during the design process.
This may be different for properties within a conservation area, and planning permission may be required. If you are unsure whether your design falls under permitted development regulations, we will be happy to discuss this with you during the design process.