I recently changed my garage to a store room/utility area. SBC Building Control were involved because they had to ensure the correct drainage and damp proof course was maintained.
I have to say the Building Inspector was very helpful and paid several visits during the process to ensure proper compliance. Nothing was unduly delayed due to having to wait for him. On completion of the work, a certificate was provided and is now part of my conveyance pack should I ever wish to sell my house.