Tony wrote:

Does anyone have any experience of fitting these silly hoods? They are
adjustable, but even at the minimum size they are too big. I've trawled
the manufacturers for smaller hoods, but the only one I found (from
Hotpoint) was extortionate.

I know what you mean; I've fitted three of these hoods in the past
couple of years and in each case the 'minimum' size was too big!

Presumably you have two telescoping sections? I just threw one away,
and cut the other to the correct length using a pair of tin-snips; and
finally drilled new clearance holes in each side at the top (ie matching
the original I'd thrown away), in order to be able to attach the chimney
to the upper wall bracket. Wasn't difficult.

hth
David