Nuneaton and Bedworth Borough Council states that "Article 4 Directions are made when the character of an area of acknowledged importance would be threatened" and that "The issuing of an Article 4 Direction means that planning permission is required for work which normally does not need permission, in an area specified under the Direction", adding that an owner can check with the council if unsure. It names the Abbey Conservation Area, now in St Mary's Ward, and holds the full list on its Article 4 Directions download page. Its works in a conservation area page covers demolition and works to trees, and says nothing about windows or doors.
The Planning Portal states that planning permission is not usually needed for the "insertion of new windows and doors that are of a similar appearance to those used in the construction of the house". It adds that "If your house is in a designated area (conservation area, national park, area of outstanding natural beauty) there may be additional restrictions in place", and that listed building consent is needed for significant works to a listed building.
On building control the same source states that "Since 1 April 2002 building regulations have applied to all replacement glazing", and gives two routes: "an installer registered with the relevant competent person scheme", who provides a certificate on completion, or an unregistered installer or do it yourself, "in which case approval can be sought from the relevant Building Control Body".
We would explain how you check the conservation boundary, any Article 4 direction and the proposed work before confirming whether permission is needed, then name the competent person scheme you are registered with and what its certificate covers.