Generally, you will need to obtain planning permission for the installation of traditional windows. This is because they are big items which are highly visible and therefore usually considered an adornment to your property. The size restrictions are usually set out in the national planning policy framework and these are half a metre above your window sill or 2 metres if it’s a larger window like a living room bay window.
The main issue with planning is likely to be at what point the planning authority consider your house to ”look like” a new build as opposed to a traditional-looking one. In most cases, this usually requires planning permission for alterations.