In article , "Owain"
says...
snip
Removing the chimney breast without supporting the stack above is probably
the most common cause of "I did some DIY and the house fell down" stories,
and builders cannot be relied upon to do the job properly on their own
initiative.

Did you see that cowboy builder programme a while ago where someone
had "supported" the stack with a bit of 4x2? :-0