John K wrote in message ...
I heard that an extension/conservatory has default planning permission
after a certain period of time, even though originally constructed
without planning permission and outside permitted development. Is this
true?
Not true.

What impact does such entensions/conservatories have when the house is
up for sale? How do you prove that they have default planning
permissions?
Ask the local authority building control department.

A general FAQ that would apply is he
http://www.bathnes.gov.uk/buildingco...nsanswered.htm