When you’re buying a listed building how can you be sure the owners have not done work without geting the proper permissions?
You can look up on the council’s building control site and see if there’s anything there but there are specialist surveyors who’ll help you.
Two points out of many that this surveyor will take into account when looking at a listed building are:
Historic documentation relevant to the property including the setting of the property
Unlawful alteration works undertaken by current, or previous owners