Do not ignore flats in cities covered by multiple postal codes
For example, there are three postal codes in Rennes associated with the same city "Rennes" : 35000, 35200, 35700.
When doing a postal code through city name lookup, either one of these three might be used. Suppose we get "35200" but the flat really is in "35700" postal code.
If the user only requested flats from "35700", the flat will be (incorrectly) discarded.