Now that you know that the work is unsatisfactory you are going to have to
disclose the fact if you sell. Therefore you need to get it sorted for that
reason quite apart from the safety aspect. The problem in seeking redresss
from the previous owners is dependant on adeqaute proof. If it came to a
court case then you would have to prove that the previous owners lied to to
you. It would be worth having a quick word with your solicitor to see if he
confirms my feelings.

Peter Crosland