The Southern Upland Way is Britain’s first official coast to coast long distance footpath. It runs 214 miles (344 km) from Portpatrick on the south west coast of Scotland to Cockburnspath on the eastern seaboard. It offers superb and varied walking country, still undiscovered by many enthusiasts.
The Southern Upland Way is the course for a long-distance race, where the supported FKTs have been set. See the race website for more information: https://www.gbultras.com/ultra-great-britain/ As of 2021, the website lists the FKTs as:
Jack Scott (GBR) 55 Hours 42 Minutes (2020)
Anna Rutherford (GBR) 62 Hours 34 Minutes (2021)
GPX files are available here: https://www.traildino.com/trace/continents-Europe/countries-United_Kingdom/states-Scotland/trails-Southern_Upland_Way