WANTED: Self-contained workspace/office space

Hi! I'm looking for a small building or room to use for quiet, solo work during the day. I would be doing computer work, with no visitors, and I would not be sleeping here. I'm looking for something very quiet, ideally self contained and not above or below another floor used by others. For example a converted garage, small office annex, or a small single-storey side extension.

Please get in touch if you have anything in the areas included. :)