Walsall Council states that "Article 4 directions withdraw certain permitted development rights to give extra protection to certain properties, such as removal of timber windows, doors and chimneys", and that "This means that you have to submit a planning application for work which may not normally need one." Its page names eight buildings and areas with directions in force, Highgate, Great Barr and Bourne Vale among them, and records that "An Article 4 Direction has been implemented for smaller HMO in the whole of the Walsall borough." It asks owners to "contact us to discuss them with the conservation officer".
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", and that "a new bay window will be treated as an extension and may require permission". It adds that a listed building needs listed building consent for any significant works.
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 the scheme you are registered with, and what the certificate covers, in the same plain words.