Inserting a window in your house
If the window projects beyond an existing wall (such as a bay window), this is treated as an extension and is subject to the same restrictions as extensions and additions.
First floor and above windows
If the window you want to insert is upper-floor window and in the side elevation of the house, it must be obscure glazed and non-opening. (Unless the opening parts of the window are more than 1.7 metres above floor level.)