I had asked for a 2 section UPVC window for my bathrooms. Bottom section fixed glass and the top "pull and lift" (think its called casement). The company bungled and gave me a bottom section fixed glass but the top section had nothing but a cardboard. The windows have been installed and so not much can be done now. Can a exhaust/glass ventilator be fixed within the existing upvc frame. I cant have a fixed glass as the room needs some ventilation. Removing the windows and getting new ones installed is not an option. Any help the experts can provide is much appreciated.