Thank you for your question, apologies for not getting an answer to you sooner.
In a single storey extension the stove fitting and requirements are much the same as in any other building.
The stove needs a flue of around 5 metres for the perfect draw to allow your stove to function to it's maximum potential.
The chimney attached must adhere to the current building regulations document (link below).
We would recommend getting a site inspection from a HETAS registered stove installer, he will be best placed to see the extension and will be able to advise on all aspects of planning. He will also be able to sign off your finished installation and provide certificates for local authority and insurance companies etc.
Find a HETAS installer here - http://www.hetas.co.uk/find-installer/
Hope this helps?