The reliable way to hire a tradesperson

I'm planning to buy a 2020 semi, that has had an extension fitted across part of the rear in 2023. The builder appears to have concreted over 2 of the 3 periscope vents that ventilated the suspended concrete floor in the house. There are 3 vents at the front but just 1 in the corner of the rear. Should I avoid this house or cam this be fixed? Will it be causing issues under that floor?

I would be extremely grateful for any advice you could give me with the following.  I am trying to refurbish the floors of my 1979 1st floor flat. After having to break out an area of cracked original concrete screed I have exposed what I think is an old paper 'slip sheet' or debonding layer which was laid under chicken wire that must have been the base for the original screed. There are still patches where the screed is very crumbly and loose and the entire screed subfloor appears to be floated over the paper layer which is separating it from the structural concrete beneath.   How can I repair this area in preparation for a layer of SLC? I am concerned about pouring a liquid screed over the exposed paper. kind regards

I HAVE DUG THE FOUNDATION FOOTINGS FOR INSTALLATION OF A PATIO . Unfortunately,one of the post footing lands smack bang over pvc sewer pipe to house..I cant change the location of posts.Suggestions on how i can protect the pipe while having the patio post over it?