GeoJSON MultiLineString import to MySQL with SRID/CRS 27700, 'out of range'
The way I've found to work around this to use ogr2ogr to import the eastings and northings (in a geojson file). An example code would be as follows:
ogr2ogr -f MySQL MySQL:test,user=root import_file_location \
-nln FILENAME -update -overwrite -lco GEOMETRY_NAME=MULTIPOLYGON

This will import as British National Grid coordinates, which can then be used to create buffers in MySQL.