When I lived in France, I built several chimneys using terra cotta chimney blocks looking something like this. They basically form a full height chimney that will go up a good 10m or more, and just stack one on top of the other with a good dollop of mortar to join them. They go up really quickly, and work a treat. You can punch a hole in the side of one of them to either vent the smoke from a wood burner directly into the pipe or you can drop a flexible flue liner down them and attach that to the wood burner through the hole punched in the side. Does anyone know whether these can be bought in the UK? Are they approved for use in the UK? What would they be called in the UK?