4

Wow rather too much information.

The bounding box you are querying and the scale you are using will never deliver good query performance. Neither the planet_osm tables nor the mapnik stylesheet are designed for rendering a large area including Belgium, London, the outskirts of Paris, and most of the Netherlands at this scale. Your bounding box approximates to this tile http://b.tile.openstreetmap.org/6/32/21.png. As you can see Mapnik on the main site renders very few features for this bounding box (largely roads from the planet_osm_roads table).

You queries include some detail information (e.g., picnic sites).

The main mapnik stylesheet is probably best regarded as optimised for mid-scale and large-scale maps.

SO, briefly, if this is what you want to do, you’ll have to live with the performance.