With a limited number plastic extruders the key difference between window and conservatory suppliers is the quality of work from the fitters and the after service should something go wrong. After 4 years of service a roof leak developed when the snow came. The fault was caused by a long dark grey stretch of gutter warping in the summer heat and coming away from the wall. This allowed the snow to melt down the back of the gutter and water came through the front section of the roof. DWL were straight round and fixed the problem without and delay all under warranty.