Hi, not sure if I can help but I can provide some general advice-
Based upon your photo of the dormer it looks like the potential conflicts with the
PD legislation are as follows:
1. The dormer may extend beyond the boundaries of your property as the party walls have been built up. Some councils will take the view that development can only be PD if it is entirely contained within the boundaries of a single dwellinghouse.
2. The dormer is not set back 200mm from eaves and you will probably struggle to convince the council or an Inspector that this was not practicable. The set back would have been achieved but would have increased the cost of the build- in most cases like that I have seen Inspectors have taken the view that the dormer does not comply with PD legislation.
3. Materials- these should be of a similar appearance to those used in the construction of the exterior of the existing dwellinghouse. Not sure from the photos how close a match the tiles and walls are, the windows are brown framed which is not a similar appearance to the white framed windows of the house. It looks like the council have not raised this issue but an Inspector may do if you end up at appeal.
Your main options moving forward are:
1. Wait and see if the council does actually decide to serve an enforcement notice. They may not and if so after 4 years the dormer will be immune from enforcement action. If they do you can appeal on various grounds and may succeed. If the appeal is dismissed you may have to remove the dormer or carry out works to make it PD compliant.
2. Apply for planning permission for the dormer and appeal if it is refused. If the appeal is dismissed you can then move on to option 1.
3. Carry out works to make the dormer PD compliant. If you are going to do this it may be worth applying for a LDC for the revised dormer design just to be 100% sure the council are happy that it complies with the PD legislation before you spend money on further works.