I've installed two chimneys and the flues in my bungalow for wood burners. The first step is to decide where you want the stove relative to the eves and make sure that you have clear space above so that the Double wall conduit will pass through the joists etc to just under the ceiling.
Second Choose a chimney stack from Poujoulat. this is an example.
You will need single wall tube grom the stove to just under the ceiling, if you have your stove you will know the size you need, I would recommend a telescopic tube so that you can easily remove it for maintenance etc.
Go to your local Toute Materieux builders merchants armed with a sketch showing your roof angle, the distance from the centre line where you want the stove and the distance from the outside wall so that they can calculate how much tubeage and what adaptors, you need and arrange delivery from Poujoulat.
You can order the chimney at the same time.
Remember to have a stiff drink before you visit to lessen the shock!