On 11 Feb, 07:59, " wrote:
My misunderstanding - I read it as meaning they had installed an
undersized stainless steel liner of a grade not intended for solid
fuel use.

I believe the flue to be fit for purpose. There's even a box on the
HETAS form for a cast in situ liner. The more I think about it, the
more I'm of the opinion that the company has let that part of their
HETAS registration lapse, and are covering their backs.

The irony is that the company is called something like
CastInSituLiners-R-Us and are part of a national franchise network of
the same name.

Nevertheless, fraudulent HETAS forms are one thing, not providing
external combustion air is quite another!