Lichfield District Council states on its own advice page: "If your property is in a conservation area/ an area covered by an Article 4 Direction, you will need to apply for planning permission to install new windows and or doors, so that we can advise you." It adds that "The materials you use for new doors and windows will need to be of a similar appearance to those already on the property", and that "If you live in a listed building and want to install new windows or doors, you will need to apply for listed building consent."
It counts "21 conservation areas in Lichfield District" and records "3 Article 4 directions which affect certain properties within the Lichfield City Conservation Area, the Whittington and Wigginton Conservation Areas." Among the works it lists as needing permission as a result of a direction is "the installation or alteration of windows and doors".
The Planning Portal states that "An external window or door is a 'controlled fitting' under the Building Regulations" and that "Since 1 April 2002 building regulations have applied to all replacement glazing". It gives two routes: "an installer registered with the relevant competent person scheme", who is "approved to carry out the work to comply with building regulations without involving local authority building control" and hands over 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".
GOV.UK states that "You can join a 'competent person scheme' to self-certify certain types of building work if you work in the building trade as an installer. This is instead of getting building regulations approval", and names Blue Flame Certification, CERTASS, Certsure, Fensa, NAPIT and ASSURE for replacement windows, doors, roof windows or rooflights in existing dwellings.
We would explain how you check the conservation boundary, any Article 4 direction and the proposed work before confirming whether permission is needed, and name the scheme you are registered with beside it.