Resource for scientific maps?
Most maps of Great Britain derive from the maps published by Her Majesty's Ordnance Survey.  The official website is https://www.ordnancesurvey.co.uk/ and the sales page says that for £23.99 you can get a 1 year subscription to a digital app that gives you the ability to export in the GPX digital format.
A crowd sourced version working on a map of the world is The Open Street Map Project.  This is equivalent to your rejected option of Wikipedia but I mention it for others that may land on this question.