"my understanding of Polish law"
Is not the same as EU law.
I will give you an example of Polish law.
I had a building constructed. I used two seperate building companies, one for the main structure and roof and the other for the finishes. During construction it was noticed that the "headroom" at the top of the stairs was a bit inadequate, the architect met the builder on site and decided to put a small "dormer" plus a small window into the roof, this to increase the headroom and also to allow more light into the stairwell. All was agreed and the architect made a note in the "building book" as to the minor change.
The second builder arrives on site and completes all the finishes to a very satisfactory standard.
The local building control attends the site to "sign off" the building and "legalise" it.
On inspection they notice the small dormer and window (not above existing roof height) and refuse to sign off the building as this additional work is not in the project
, they also fine me 3000PLN.
I contact the architect who goes to see the building control and she is unable to convince them that this minor ammendment does not need permission.
The obvious choice for me is to get the architect to re-do the drawing and apply for retrospective planning permission which takes about 2 months. The architect does the drawing and insists on being paid again for this work. I explain that there is a fine to pay and I will hold her responsible to pay this.
On taking legal advice from a lawyer friend who actually teaches law, it seems that I cannot sue the architect. According to Polish law, I have to sue the last contractor on site., the one who did a perfect job for me and had nothing to do with the construction of the roof. Total cost of delays and fines, around 50,000 PLN, and, yet again, nobody is responsible.
As this money is coming out of my pocket, it must be my fault.
This is Poland.