text: Yes, correct, then you need to create entrance nodes.  I find GRB data actually quite accurate, the more issues I got reported, the more I think it's pretty good quality.  If it has the same street, you could use addr:flats + addr:housenumber, depends on the type of 'split' you can make.  But if you don't know the door/entrance, you should put them all seperated by ;   we should really not tag for the renderer,    on the contrary, we need to tag as we should and let the mapstyle people deal with real life issues when displaying housenumbers.  (reverse/g+ geocoding works fine with those numbers)
  