I would like to know more about your twin wall flue

We stock and pick our own twin wall Clearline AKW flue pipe. This can be used to form chimneys in existing and new houses and be run 50mm from combustible materials. It fits together very easily and there are components to take it through floors and roofs. 

We have a number of pages of information about this flue , the best place to start is the main Double skin flue page