The Ferretería in Camarles on the left as you come in or the right just on the edge of town on the N340.He has stock in the window. Take a small section of pipe or a piece of string the same circumference to assist as they vary. The pipes come in black and plain galvanised.What you should have is double skinned on any pipe that leaves the house and is subject to outside cold air as this cools the gases and leaves a crusty black solid tar crystals that will block your chimney.Remember any pipe should be male pointing down so that any tar runs in the pipe not on the outside wall. Nigel knows a supplier of the double and single skinned stainless steel pipe I can not remember the location it is rather expensive. Most is made in Spain  ::)

Below is an English web site that will answer any questions you may have and give you an idea of stock.You can always run a copy of the pipe you want which may save on the Spanish. :-[

http://www.fluesupplies.com/index.php?cPath=24_59