If you are relining your chimney whether that be with flexible liner, pumice, or concrete liners or if you are building a new chimney (including building a new chimney using twin wall insulated flue pipe) then this is classed as "Building work" and you must notify building control before work starts.
In any case there may well be local planning restrictions convering chimney work and new chimneys that you have to follow.
Such work has to be done under the guidance of a building inspector or by an installer who is a member of a "Competant Person Scheme". You can find more information on the Competent Person Scheme on our stove installers page
In most instances a new chimney can be erected under permitted development (in accordance with Class G, Part 1 of the Town and Country Planning (General Permitted Development) (Amendment) Order 2008).