John Kelly wrote:
We're about to put in a wood burning stove. We have a modern house with
a crap chimney so it'll need to be lined. Will we need some kind of
airbrick anywhere and where would be best to put it if we do?

You will need some form of ventilation. The nearer to the fire it is the
less draughts there well be. If you have a ventilated underfloor space
consider a grille in the hearth going onto it. This is mandatory from
building control point of view. Its size can be ascertained by looking
into the relevant building regulations.



We also need cavity wall insulation doing at some point as we found out
it hasn't got any when we had the extension built despite it being on
the original house builders info (from 20 years ago).


That is a statement, not a question...