Hi Wicked Sunday! HERE, I already gave you some tips on how to search successfully, respectively how I search. Honestly, I don't know what else I could advise you otherwise.
You don't live very far from Belgium. There is a very big and active UE-scene there, and in BE are also hundreds of abandoned places. So it shouldn't be too difficult to make contacts there and / or to find abandoned places in BE. The web is full of it; sometimes even with quite helpful descriptions or information, that can be used to find the places with a little search.
And regarding the sorting: Why should the places be sorted by country? After all, Oblivion State is NOT primarily a forum to find places, but a community, to SHOW photos & reports of visited places (of course, too, to view and comment on others' pics and posts, etc.).
In this regard, each has their own preferences and interests. And these usually don't refer to where a place is, but ordinarily based on, what kind of an abandoned place it is (some prefer castles or villas, other industries, others mines, bunkers and caves and so on). Concerning this personal likes, many look specifically at relevant albums and posts.
For this reason, the deliberate chosen categorization here by the kind of places is expedient, and it will hardly be changed into a sorting by countries, I think. At least that's my opinion.