The National Library of Scotland has a range of UK maps online. These are useful resources for identifying the historical location of buildings and features in the landscape. The library also has tools which enable you to compare and overlay maps. Many of the maps on the website can be used for commercial, non-commercial, educational and private purposes under the terms of the Creative Commons license.
The National Library of Scotland webpage: https://maps.nls.uk
For more information on the Creative Commons , see: Creative Commons Attribution (CC-BY) licence