Five trips to the UK since 2001, nine to Europe, most of what I've seen of RV camping, particularly motorhome camping, has been close together parking in a field, or on a parking lot, with little in the way of hookups. In some places these are clearings designated for RVs, in others it just looks like they've taken over a more general parking lot. And sometimes, shopping center parking lots, and highway rest stops.
Most crowded I've seen have been along waterways in Germany. Maybe they have the greatest number of motorized RVs and the least amount of space for their use. I have caravaning guides for France that list different categories, including campgrounds, public parking areas, and RV parks with facilities and amenities. There is at least one RV park in Rome, not too far outside the city walls, but it looks like a parking lot.