We are buying a house built in 1974. The house is a repossession with no documentation regarding a room in the roof with a dormer built in 2003. When plans were submitted in 2003 for the room in the roof the plans were withdrawn from the Council. Thus I assume the then owner went ahead and built the extension without permission. The room is very well built and has no apparent issues. It faces the garden.
I don't know what problems will emerge in the future regarding retrospective permission