I forgot a few things...
You do need Building Control Approval to take down a chimney breast. If it's on a party wall you also need to comply with the Party Wall Act.
and when they fall down they actually fall over and take the wall and roof with them...
Some googling reveals it's the third most common cause of building collapse...
http://www2.halton.gov.uk/content/environment/planning/buildingcontrolconsultanc... Quote: Our surveyors have found that the most common causes of collapse are:-
*Removal of lateral restraint to walls.
*Failure of over-stressed piers.
*Inadequate support to chimney breasts.
http://www.lawteacher.net/Contract/Contents/Exclusion%20Clauses%20Cases.htm Quote: The surveyor negligently failed to check that a chimney breast which had been removed was properly supported. When the chimney collapsed the plaintiff sued the valuer.
http://www.glias.org.uk/news/195news.html Quote:Building collapses
Considerable disruption resulted following the partial collapse of a Victorian terraced shop in the Blackstock Road, Islington....<snip>... Renovation by insufficiently skilled builders can be quite a hazard. In this case it was probably work on a chimney breast which caused the problem.