I have a decorative gas fire, installed by british gas in about 1987,
in the living room fireplace. It uses the existing (unlined) flue.
IIRC, it's 6kW heat input, but being a decorative fire, it does
generate some soot. Since installing central heating, it's only been
used extremely rarely (for decoration), but it's a feature of the
room, and not one I'm planning on getting rid of.

If this was being installed today, would a flue liner be recommended
or even mandatory?
Reason for asking is that I currently have scaffolding right up to
the chimney pots, and in the interests of bringing it up to current
standards, it would probably be easy to do at the moment. If so,
what sort of flue liner?
Do flue liners always result in an ugly bit of metalwork sticking
out of the top of the chimney?
With a flue liner in place, how does ventilating the inside walls
of the original flue work? Do you add vents to the top and bottom
of the original flue to allow airflow around the outside of the
liner?

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]