Re: Buying a house with no Planning Permission or Building regs for extension
This is probably best for a surveyor to answer. You would need to be able to identify the work that has been done already without Building Regs consent, apply for retrospective consent and open up those works so they can be checked for compliance. This may be possible to cover as part of your proposed work, but it all depends on what has been done and what you propose to do.
This is based on my experience as a conveyancing solicitor in England, but I do not accept liability for information I give in this forum