The XY coordinates must be provided in OSGB/British National Grid (Lat, Long) format
in the README (line 127) could be a bit confusing - the grid references it refers to aren't degrees of latitude or longitude (either decimal degrees or degrees/minutes/seconds), and the order of coordinates is actually (X, Y), ie (long, lat)
Just a note that the line
in the README (line 127) could be a bit confusing - the grid references it refers to aren't degrees of latitude or longitude (either decimal degrees or degrees/minutes/seconds), and the order of coordinates is actually (X, Y), ie (long, lat)