Inspired by rfuerst911sc's thread and reading about other Pelican building projects I thought I'd start my own UK edition
To set the scene my house is in a small rural village at the cheap end of the Cotswolds which is a designated Area of Outstanding Beauty in the middle of central England
My house is in a 'Conservation Area', Local authorities can designate an area of special architectural or historic interest whose character or appearance is worth protecting or enhancing which means approval for building developments is harder to get.
First step is to submit plans to my local planning authority. Drawings consist of all elevations and floor plans as the house is and then same again but showing the proposed changes. These have to be approved first by the village council and then by the local authority.
First attempt was rejected

a porch entrance to an office above the garage was visible form one elevation and they didn't like how it looked. The planning officer was very helpful and suggested a few alterations to make it acceptable for approval.
2nd attempt they were approved, always one to make an opportunity from a set back I made a few changes to my man cave part of the layout that will make it far better than I had ever envisaged

Thank you Mr Planner, much appreciated.
This is my house before work started,
Late 18th C, constructed from local Hornton stone (much darker than the light Cotswold stone), 2ft thick walls, roof was originally thatched but now has moss covered concrete tiles from the 70's. Bought in 1996 in a very poor condition and lovingly restored over many years.