Sir: Unlike Teresa Gorman, my experience of the process has had its lighter moments.
In 1986 I purchased a late 16th-century timber-framed farmhouse (unlisted). In 1991 and after extensive repairs and modifications, the powers that be decided that my efforts deserved Grade II listing. As I had done most of the work myself I felt rather proud of my talents, particularly when I read the fine print of what had been actually "listed".
Back in the early 19th century, one wing burnt down and was replaced by an early Victorian brick structure. Some time in the recent past, a previous owner had constructed a wall-to-wall, split-level, artificial stone fireplace "feature". I ripped it out, rebuilt the chimney breast and hearth, fitted an antique tiled fireplace and finished it off with a wooden surround from B&Q.
Yes, you've got it, my DIY fireplace is now Grade II listed.